Carotenoid isomerase activity and carotenoid content maintain the appropriate tiller number, photosynthesis, and grain yield. Interactions between the strigolactone and abscisic acid pathways regulates tiller formation. Tillers are unique inflorescence-like branches in grasses, and their number determines the panicle number, plant architecture, and yield (Shang et al., 2021). Tiller formation mainly undergoes axillary meristem (AM) initiation and tiller bud outgrowth (Wang et al., 2018; Yan et al., 2023). The rice (Oryza sativa) KNOX gene OSH1 is expressed in AMs, and an osh1 mutant produces fewer tillers (Tanaka et al., 2015). LAX PANICLE 1 (LAX1) contributes to establishing AMs, and its mutation affects AM initiation, leading to fewer tillers like the osh1 mutant. MONOCULM 1 (MOC1) and MOC3 are additional key regulators of AM formation in rice. The moc1 mutant fails to form axillary buds and tillers, and OSH1 is no longer expressed in moc1 AMs (Li et al., 2003). Axillary buds and tillers fail to form in the moc3 mutant. Furthermore, MOC3 interacts with MOC1 to promote tiller bud outgrowth by activating the expression of FLORAL ORGAN NUMBER 1 (FON1) (Shao et al., 2019). Carotenoids are precursors to the phytohormone strigolactones (SLs) and inhibit tiller bud growth (Gomez-Roldan et al., 2008). Similar to other phytohormones, such as auxin and brassinosteroids, the genes involved in SL biosynthesis and signal transduction play an important role in regulating tiller bud outgrowth (Gomez-Roldan et al., 2008; Yin et al., 2022; Li et al., 2023). MORE AXILLARY BRANCHES 3 (MAX3, also named HIGH-TILLERING DWARF 1 [HTD1]) and MAX4 (also named DWARF 10 [D10]) encode carotenoid lyase diaoxases CCD7 and CCD8, respectively, and participate in SL biosynthesis (Arite et al., 2007). In Arabidopsis (Arabidopsis thaliana) and rice, branch number changes upon mutation of CCD7- or CCD8-like genes, suggesting that SLs are conserved regulators of branching in dicots and monocots. The F-box protein D3, a rice homolog of Arabidopsis MAX2, interacts with D14 and D53 upon treatment of rice seedlings with SLs, leading to the ubiquitination and degradation of D53, and thus the inhibition of tillering (Wang et al., 2018). HTD1 inhibits tiller bud outgrowth and tiller formation, and its beneficial alleles were widely selected, which promoted the Green Revolution of rice breeding (Wang et al., 2020). In this study, we report that DUONIE (DN) regulates tillering and grain size via the carotenoid biosynthesis pathway. We obtained the dn mutant that produced more tiller buds and exhibited a faster elongation of tiller buds, resulting in plants with more tillers than the wild-type (WT) (Figures 1A, B, S1). In addition, the dn mutant had a dwarf stature, shorter panicles, fewer branches and grains, and lighter grains (Figures 1A–D, S2, and S4). These results suggest that plant architecture and grain productivity are disturbed in the dn mutant. Phenotypic characteristics of plants, regulation of strigolactones (SLs) and abscisic acid (ABA) on tillering, and enzyme activity assay (A) Tiller phenotypes of the wild-type (WT), dn mutant, knockout lines knockout (KO)-1 and KO-2, overexpression lines overexpression (OE)-2 and OE-3 at tillering stage. Scale bars = 10 cm. (B) Tiller number of the WT, dn mutant, knockout lines KO-1 and KO-2, overexpression lines OE-2 and OE-3. (C) Grain length of the WT, dn mutant, knockout lines KO-1 and KO-2, overexpression lines OE-2 and OE-3. Scale bar = 1 cm. (D) Grain width of the WT, dn mutant, knockout lines KO-1 and KO-2, overexpression lines OE-2 and OE-3. Scale bar = 1 cm. (E) Purification of DN and dn proteins from Escherichia coli. (F) Enzyme activity assay of DN and dn in vitro. L1 and L2 represent DN fused to glutathione S-transferase (DN-GST) protein, L3 and L4 represent dn-GST protein, and L5 and L6 represent GST protein. (G) Total enzyme activities in the WT and dn seedlings. (H) Immunoblot analysis of DN. Total proteins were from WT and DN (fused GFP-tag) overexpression seedlings (OE-2 and OE-3). Chloroplast proteins were from OE-2 and OE-3. Antiserum against GFP-tag, β-actin, and Lhcb5 (chloroplast marker) were used in blotting. (I) The seedling phenotypes of WT, dn mutant, and DN overexpression lines. Scale bars = 1 cm. Dark: 6 d indicates that the seedlings were placed under darkness for 6 d. Light: 5 h indicates that the seedlings were exposed to light for 5 h after darkness. (J) The content of photosynthetic pigments in leaves of seedlings of WT, dn mutant, and DN overexpression lines. (K) Concentrations of photosynthetic proteins detected in total proteins in the dn mutant, WT and DN overexpression line OE-2 seedlings under darkness (10 d) and recover light (5 h) treatment. Antibodies are indicated on the right. (L) Tiller bud of the WT, dn mutant, and overexpression line OE-2 seedlings. Scale bar = 1 cm. (M) Tiller bud of the WT, dn mutant, and overexpression line OE-2 seedlings with rac-GR24 (The SL analog) treatment. Scale bar = 1 cm. (N) Tiller bud of the WT, dn mutant, and overexpression line OE-2 seedlings with ABA treatment. Scale bar = 1 cm. (O) Comparison of expression levels of SL biosynthesis pathway genes in stem bases after ABA treatment in WT and dn mutant. (P) Comparison of expression levels of ABA biosynthesis pathway genes in stem bases after rac-GR24 treatment in WT and dn mutant. (Q) Work model of carotenoid biosynthesis pathway control tillering and grain size in the WT rice. Normal levels of carotenoid isomerase and carotenoid content maintain the appropriate tiller number and grain size. The SL–ABA interaction pathway regulates tiller formation. Strigolactone promotes ABA biosynthesis to regulate tillering, and ABA represses SL biosynthesis. In addition, carotenoid isomerase might contribute to maintaining normal photosynthesis for grain yield by affecting greening capacity. (R) Work model of carotenoid biosynthesis pathway control tillering and grain size in the dn mutant. Defective of carotenoid isomerase and reduced carotenoid content lead to multiple tillers and small grains. The ability of ABA to inhibit SL biosynthesis was weakened. In addition, defective carotenoid isomerase might depress the rice greening capacity, which might be one of the reasons for the lower productivity than WT in dn mutant. The asterisk and double asterisks represent a significant difference, as determined using Student's t-test at P < 0.05 and P < 0.01, respectively. To identify DN, we generated a segregating F2 population by crossing the rice cultivar TN1 to the dn mutant, delineating the DN locus to the 71-kb region on chromosome 11 (Figure S3). DNA and coding sequence (CDS) sequencing of the annotated genes in this interval revealed a 4-bp deletion in the seventh exon of Os11g0572700 in the dn mutant, resulting in premature translation termination (Figure S3). We thus speculated that the mutation of Os11g0572700 is responsible for the effects on tillering and plant architecture of the dn mutant. To test this hypothesis, we obtained a CRISPR/Cas9-mediated knockout (KO) and overexpression (OE) lines. The resulting KO1 and KO2 knockout plants produced more tillers, smaller grains, and shorter plants, similar to the dn mutant (Figures 1A–D, S2, and S4). The OE2 and OE3 lines showed the opposite phenotypes, with fewer tillers and larger grains (Figures 1A–D, S2, and S4). We conclude that Os11g0572700 (DN hereafter) is the gene mutated in the dn mutant and that DN negatively regulates tillering and positively controls grain size in rice. DN encodes a carotenoid isomerase (CRTISO). We asked whether the dn mutant influenced carotenoid isomerase activity. Indeed, we measured lower CRTISO activity in protein extracts from dn seedlings compared with WT seedlings (Figures 1E–G, S5). We also produced and purified recombinant DN fused to glutathione S-transferase (DN-GST) and dn-GST to perform an in vitro CRTISO activity assay. Purified DN-GST exhibited a high carotenoid isomerase activity, in contrast with the low activity displayed by dn-GST (Figures 1E, F, S5). These data suggest that DN is a functional carotenoid isomerase, and the dn mutation abolished its activity. To assess DN expression, we performed an RT-qPCR analysis and detected DN transcripts in all tissues tested (Figure S6A). We also examined which organelles DN accumulated by transfecting rice protoplasts with a construct encoding a DN-green fluorescent protein (GFP) fusion protein. We exclusively observed GFP fluorescence in chloroplasts (Figure S6B). In a complementary approach, we conducted an immunoblot analysis on total protein extracts and chloroplast fractions from WT plants and DN-overexpressing lines, which confirmed the localization of DN to chloroplasts (Figure 1H). CRTISO-like enzymes are widely present in plants, encoded by one or two genes in most plant species (Figure S8A), suggesting that this enzyme is functionally conserved. CRTISOs convert cis-lycopene to all-trans lycopene, thus affecting carotene production (Liu et al., 2020). To explore whether DN participates in carotenoid biosynthesis, we measured the carotenoid content of WT and dn seedlings and detected lower carotenoid content in the dn mutant (Figure S7A). We also measured lower all-trans lycopene content in dn, while the DN-overexpressing lines accumulated more all-trans lycopene than the WT (Figure S7B). We performed an RNA-seq analysis on WT and dn seedlings, which revealed the differential expression of genes involved in phytohormone biosynthesis (Figure S8B, C). We analyzed the transcript levels of carotenoid biosynthesis genes, including DN, PHYTOENE SYNTHASE 1 (PSY1), PSY3, TILLERING 20 (T20), ZETA-CAROTENE DESATURASE (ZDS), PHYTOENE DESATURASE (PDS), and LYCOPENE Β-CYCLASE (LYCB). Most genes in the dn mutant had lower expression levels (Figure S9A, B). In agreement, etiolated dn seedlings remained yellow after exposure to light, whereas etiolated WT and DN-overexpressing seedlings turned green (Figure 1I, J). To determine to what extent modulating carotenoid biosynthesis via the dn mutation or DN overexpression affected chloroplast development, we assessed the abundance of core subunits for photosystems I and II (PsaC, Light-harvesting complex a2 [Lhca2], Lhca3, PsbA, Lhcb4, and Lhcb5) using immunoblot analysis (Figure 1K). We detected lower levels of these proteins in etiolated dn mutant seedlings transferred to the light, in contrast with DN-overexpressing seedlings, which accumulated more of these proteins than WT seedlings (Figure 1K). These findings reveal that DN is a chloroplast-localized CRTISO whose loss of function prevents carotenoid biosynthesis. Carotenoids are the precursors of SL and abscisic acid (ABA) biosynthesis (Zhou et al., 2021). As carotenoid biosynthesis was defective in the dn mutant, we speculated that SL and ABA biosynthesis may be disrupted in this mutant. We therefore investigated the expression levels of SL biosynthesis and signaling-related genes. The expression levels of D3, D10, D14, D17, D27, and D53 in dn were much lower than in the WT (Figure 1O). We also determined SL levels in the WT, the dn mutant, and the DN overexpression lines at the seedling stage. The dn mutant accumulated less SL, whereas the WT and DN overexpression seedlings had higher SL contents (Figure S7C). Together with the lower expression levels of SL biosynthesis in dn, we concluded that DN is involved in SL biosynthesis (Figures S1O, S7C). We performed a similar analysis for ABA and ABA biosynthesis genes. We measured lower ABA levels in the dn mutant relative to WT, with higher ABA content in the DN overexpression lines (Figure S7D). We also assessed the transcript levels of ABA-inducible and biosynthesis genes ABA DEFICIENT 1 (ABA1), ABA2, ABA3, NINE-CIS-EPOXYCAROTENOID DIOXYGENASE 2 (OsNCED2), OsNCED3, OsNCED5, and hox gene OsHOX12. ABA1/2/3 and NCED2/5 were expressed at lower levels in the dn mutant compared with the WT (Figure 1P). These findings indicated that DN is required for SL and ABA biosynthesis. We hypothesized that SLs and ABA might contribute to tiller bud outgrowth. Accordingly, we used the SL analog GR24 to treat seedlings of the dn mutant, the WT, and DN overexpression lines. The dn mutant had fewer tiller buds following GR24 treatment, and the tiller buds of GR24-treated WT and DN overexpression lines grew more slowly, particularly the overexpression lines (Figure 1L, M). We concluded that treatment with exogenous SLs rescues the high-tillering phenotype of the dn mutant and that SLs regulate rice tillering. Notably, the tiller buds of all genotypes were repressed by ABA treatment, suggesting that exogenous ABA treatment partially rescued the high-tillering phenotype of the dn mutant (Figure 1L, N) and that ABA also regulates rice tillering, but not directly. The above results revealed that SLs and ABA both suppressed tiller bud outgrowth and that defects in SL and/or ABA biosynthesis or signaling may exhibit a high-tillering phenotype in rice. The 4-bp deletion identified in the CRTISO gene DN results in premature termination of translation, leading to lower carotenoid content and carotenoid isomerase activity. The transcript levels of genes related to early stages in the biosynthesis of carotenoids, ABA, and SLs were expressed at significantly lower levels than the WT, in agreement with the lower CRTISO activity and carotenoid content of the dn mutant. Previous studies have shown that zebra2, an allele of dn (another mutant of OsCRTISO), has yellow-green striped leaves and longer grains. The dn mutant produced many tillers and narrow grains with normal length, while DN overexpression yielded longer, wider, and heavier grains, together with fewer tillers. These findings revealed that DN has unique roles in regulating tillering and grain production. In addition, the multi-tiller phenotype of dn was partially rescued by exogenous ABA treatment and was fully rescued by exogenous GR24 treatment, suggesting that SLs are a major regulatory factor of rice tillering (Figure 1L, M). The dn mutant displayed decreased contents of carotenoids, SLs, and ABA. We also determined that DN expression was induced by GR24 treatment (Figure S9B). These results indicated that carotenoid biosynthesis is important for SL and ABA production and that modulating DN expression affects plant architecture and grain production by regulating carotenoid-mediated SL, ABA production, and possibly photosynthesis in rice (Figure 1I, J, Q, R). Although SLs and ABA are produced from carotenoids, their coordination has remained relatively elusive. Strigolactones were reported to induce HOMEOBOX PROTEIN 40 (AtHB40) expression and to promote ABA biosynthesis in Arabidopsis (Wang et al., 2020). In rice, overexpressing OsNCED1 led to greater ABA accumulation and fewer tillers, suggesting that OsNCED1 inhibits tiller bud outgrowth via the ABA biosynthesis pathway (Luo et al., 2019). Here, we examined the transcript levels of genes related to ABA biosynthesis. The expression of OsNCED2/3/5 and ABA1/2/3 was induced by GR24 treatment (Figure 1P). Importantly, SLs promoted ABA levels, induced OsHOX12 (homologous to AtHB40) expression, and promoted the expression of OsNCED2/3/5 and ABA biosynthesis in shoot bases (Figures 1P, S7D). Conversely, ABA treatment resulted in lower endogenous SL levels and decreased the expression of SL biosynthesis genes D10 and D27 (Figures 1O, S7C). Previous studies have reported that OsCRTISO regulated coleoptile growth by affecting ABA biosynthesis, suggesting a possible interaction between SLs and ABA (Fang et al., 2008). Strigolactones promoted ABA biosynthesis, while ABA repressed SL biosynthesis in rice. Together, these results revealed the existence of an SL–ABA interaction pathway that regulates rice tillering (Figure 1Q, R) and that is likely to be conserved in monocots and dicots. This work was supported by the National Natural Science Foundation of China (32188102, 32372118, 32071993), the Qian Qian Academician Workstation, and the specific research fund of the innovation platform for academicians of Hainan Province (YSPTZX202303), the Nanfan special project, CAAS (ZDXM2315), Hainan Seed Industry Laboratory, China (B21HJ0220), the Key Research and Development Program of Zhejiang Province (2021C02056). The authors declare no conflict of interest. Q.Q. and D.R. designed the research. D.R., C.D., Z.S., Y.Y., D.Z., Z.G., G.Z., J.H., L.Z., and G.D. performed research. D.R. and C.D. wrote the article. Q.Q. and D.R. agreed to serve as the authors responsible for contact and ensuring communication. All authors read and approved of its content. Additional Supporting Information may be found online in the supporting information tab for this article: http://onlinelibrary.wiley.com/doi/10.1111/jipb.13617/suppinfo Figure S1. Phenotypic characteristics of wild-type (WT) and dn mutant Figure S2. DN is involved in the regulation of grain and panicle traits Figure S3. Cloning and identification of DN in rice Figure S4. Identification of DN overexpression lines and knockout lines Figure S5. Protein induction and purification Figure S6. DN gene expression pattern and protein subcellular localization Figure S7. The mutation of DN affects strigolactone and abscisic acid biosynthesis Figure S8. Bioinformatics analysis of DN Figure S9. Expression levels of carotenoid, strigolactone, and abscisic acid biosynthesis pathway genes Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Chlorophyll, a green pigment in photosynthetic organisms, is generated by two distinct biochemical pathways, the tetrapyrrole biosynthetic pathway (TBP) and the methylerythritol 4-phosphate (MEP) pathway. MEP is one of the pathways for isoprenoid synthesis in plants, with 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR) catalyzing its last step. In this study, we isolated a green-revertible yellow leaf mutant gry3 in rice and cloned the GRY3 gene, which encodes a HDR participating in geranylgeranyl diphosphate (GGPP) biosynthesis in chloroplast. A complementation experiment confirmed that a missense mutation (C to T) in the fourth exon of LOC_Os03g52170 causes the gry3 phenotype. Under high temperature and high light, transcript and protein abundances of GRY3 were reduced in the gry3 mutant. Transcriptional expression of chlorophyll biosynthesis, chloroplast development, and genes involved in photosynthesis were also affected. Excessive reactive oxygen species accumulation, cell death, and photosynthetic proteins degradation were occurred in the mutant. The content of GGPP was reduced in gry3 compared with Nipponbare, resulting in a stoichiometric imbalance of tetrapyrrolic chlorophyll precursors. These results shed light on the response of chloroplast biogenesis and maintenance in plants to high-temperature and high-light stress.
The multiple organellar RNA editing factors (MORF) gene family plays a key role in organelle RNA editing in flowering plants. MORF genes expressions are also affected by abiotic stress. Although seven OsMORF genes have been identified in rice, few reports have been published on their expression patterns in different tissues and under abiotic stress, and OsMORF–OsMORF interactions. In this study, we analyzed the gene structure of OsMORF family genes. The MORF family members were divided into six subgroups in different plants based on phylogenetic analysis. Seven OsMORF genes were highly expressed in leaves. Six and seven OsMORF genes expressions were affected by cold and salt stresses, respectively. OsMORF–OsMORF interaction analysis indicated that OsMORF1, OsMORF8a, and OsMORF8b could each interact with themselves to form homomers. Moreover, five OsMORF proteins were shown to be able to interact with each other, such as OsMORF8a and OsMORF8b interacting with OsMORF1 and OsMORF2b, respectively, to form heteromers. These results provide information for further study of OsMORF gene function.
Salinity imposes a major constraint over the productivity of rice. A set of chromosome segment substitution lines (CSSLs), derived from a cross between the japonica type cultivar (cv.) Nipponbare (salinity sensitive) and the indica type cv. 9311 (moderately tolerant), was scored using a hydroponics system for their salinity tolerance at the seedling stage. Two of the CSSLs, which share a ∼1.2 Mbp stretch of chromosome 4 derived from cv. Nipponbare, were as sensitive to the stress as cv. Nipponbare itself. Fine mapping based on an F2 population bred from a backcross between one of these CSSLs and cv. 9311 narrowed this region to 95 Kbp, within which only one gene (OsHAK1) exhibited a differential (lower) transcript abundance in cv. Nipponbare and the two CSSLs compared to in cv. 9311. The gene was up-regulated by exposure to salinity stress both in the root and the shoot, while a knockout mutant proved to be more salinity sensitive than its wild type with respect to its growth at both the vegetative and reproductive stages. Seedlings over-expressing OsHAK1 were more tolerant than wild type, displaying a superior photosynthetic rate, a higher leaf chlorophyll content, an enhanced accumulation of proline and a reduced level of lipid peroxidation. At the transcriptome level, the over-expression of OsHAK1 stimulated a number of stress-responsive genes as well as four genes known to be involved in Na+ homeostasis and the salinity response (OsHKT1;5, OsSOS1, OsLti6a and OsLti6b). When the stress was applied at booting through to maturity, the OsHAK1 over-expressors out-yielded wild type by 25%, and no negative pleiotropic effects were expressed in plants gown under non-saline conditions. The level of expression of OsHAK1 was correlated with Na+/K+ homeostasis, which implies that the gene should be explored a target for molecular approaches to the improvement of salinity tolerance in rice.
As novel magnetic resonance imaging (MRI) contrast agent, gadofullerene encapsulated redox nanoparticles (Gd3NPs) were prepared by encapsulation of Gd3N@C80 in the core of core-shell-type polymer micelles composed of original polyamine with a reactive oxygen species (ROS)-scavenging ability. Because Gd3NPs possess biocompatible PEG shell with a smaller size (ca. 50 nm), they had high colloidal stability in a physiological environment, and showed low cytotoxicity. Specific accumulation of Gd3NPs in a tumor was confirmed in tumor-bearing mice after systemic administration. The tumor/muscle (T/M) ratio of the Gd ion reached five at 7.5 h after the administration. T1-weighted MRI signal enhancement of the T/M ratio increased by 8% at 6 h postinjection of Gd3NPs (Gd dose:14.35 μmol/kg). Although Gd3NPs showed a tendency for extended blood circulation, they did not have severe adverse effects, probably due to the confinement of Gd in a hydrophobic fullerene in addition to the ROS-scavenging capacity of these nanoparticles. In sharp contrast, systemic administration of Gd-chelate nanoparticles (GdCNPs) to mice disrupts liver function, increases leukocyte counts, and destroys spleen and skin tissues. Leaking of Gd ions from GdCNPs may cause such adverse effects. Based on these results, we expect that Gd3NPs is high-performance MRI contrast agents for tumor diagnosis.
Abstract Diesel composite armor has high penetration resistance and can be used in tank vehicles to improve their protective capability and increase fuel oil storage. This study provides a theoretical calculation method to investigate the interaction between a shaped charge jet and a diesel‐filled airtight structure unit. Disturbance theory can predict the part of the jet that is disturbed by diesel fuel. The lumen radius for the container was varied to study its influence on the disturbance capability. A great lumen radius is found to cause lower maximum and minimum speeds of the disturbance velocity range of the jet, as well as a narrower disturbance velocity range. The reliability of the theoretical results was validated by experiments, and the experimental data show good agreement with the theoretical results.
Leaf shape is an important agronomic trait for constructing an ideal plant type in rice, and high-density genetic map is facilitative in improving accuracy and efficiency for quantitative trait loci (QTL) analysis of leaf trait. In this study, a high-density genetic map contained 10,760 specific length amplified fragment sequencing (SLAF) markers was established based on 149 recombinant inbred lines (RILs) derived from the cross between Rekuangeng (RKG) and Taizhong1 (TN1), which exhibited 1,613.59 cM map distance with an average interval of 0.17 cM. A total of 24 QTLs were detected and explained the phenotypic variance ranged from 9% to 33.8% related to the leaf morphology across two areas. Among them, one uncloned major QTL qTLLW1 (qTLL1 and qTLLW1) involved in regulating leaf length and leaf width with max 33.8% and 22.5% phenotypic variance respectively was located on chromosome 1, and another major locus qTLW4 affecting leaf width accounted for max 25.3% phenotypic variance was mapped on chromosome 4. Fine mapping and qRT-PCR expression analysis indicated that qTLW4 may be allelic to NAL1 (Narrow leaf 1) gene.
Crown roots are essential for plants to obtain water and nutrients, perceive environmental changes, and synthesize plant hormones. In this study, we identified and characterized short crown root 8 (scr8), which exhibited a defective phenotype of crown root and vegetative development. Temperature treatment showed that scr8 was sensitive to temperature and that the mutant phenotypes were rescued when grown under low temperature condition (20 °C). Histological and EdU staining analysis showed that the crown root formation was hampered and that the root meristem activity was decreased in scr8. With map-based cloning strategy, the SCR8 gene was fine-mapped to an interval of 126.4 kb on chromosome 8. Sequencing analysis revealed that the sequence variations were only found in LOC_Os08g14850, which encodes a CC-NBS-LRR protein. Expression and inoculation test analysis showed that the expression level of LOC_Os08g14850 was significantly decreased under low temperature (20 °C) and that the resistance to Xanthomonas oryzae pv. Oryzae (Xoo) was enhanced in scr8. These results indicated that LOC_Os08g14850 may be the candidate of SCR8 and that its mutation activated the plant defense response, resulting in a crown root growth defect.
T5 pure lines of japonica rice variety Zhongchao 123 with glgC-TM gene mediated by Agrobacterium transformation,which were used as donor parent of AGP(ADP-glucose pyrophosphorylase)gene,were crossed with a nutrition-functional japonica rice variety Jupei 1 with ge gene.Sixteen lines with genes glgC-TM/ge were screened from 64 lines in F4 generation by molecular marker and morphological observation on the seed embryo from single rice plant.The physical-chemical characteristics and γ-aminobutyric acid(GABA)content of rice grains were measured for the five F4 lines with good performance of multiple traits.The results showed that all the embryo weight per 100-seed from the five F4 lines were significantly higher than that of the parent Zhongchao 123 with an increase of 70.2% at least and 119.0% at most,and the GABA content of the five F4 lines increased by 102.93% to 194.14% compared with the parent Zhongchao 123.However,the eating quality characteristics such as gel consistency,alkali spreading value and amylose content had no obvious changes in the selected lines.The amylose contents of the indicaclinous F4 lines were significantly beyond the two parents while those of the japonicaclinous ones were close to the parents,which indicated that the genes glgC-TM and ge were both expressed in the process of starch synthesis and embryo development of grains,thus leading to the increase of 1000-grain weight and embryo size.Based on these results,the breeding by molecular design combining with bio-technology and traditional technology was considered as an effective way to improve the nutrition-functional fortification and rice grain yield.
Leaves are the primary structures responsible for photosynthesis, making leaf morphology one of the most important traits of rice plant architecture. Both plant architecture and nutrient utilization jointly affect rice yield, however, their molecular association is still poorly understood. We identified a rice mutant, leaf width 5 (lw5), that displayed small grains and wide leaves and possesses characteristics typical of a small "sink" and a large "source". Map-based cloning and CRISPR-Cas9 gene editing indicated that LW5 affects both the plant architecture and yield. It is an allele of D1, encoding the rice G protein α subunit. The loss of LW5 functioning leads to an increase in the rate of photosynthesis, vascular bundles, and chlorophyll content. However, the grain-straw ratio and the rate of grain filling decreased significantly. The detection results of 15N-ammonium nitrate and an expression analysis of genes associated with nitrogen demonstrated that LW5 serves an important role in nitrate uptake and transport. LW5 affects plant architecture and grain size by regulating nitrogen transfer. These results provide a theoretical foundation for further research surrounding the molecular mechanism of "source-sink" balance in rice and suggest novel methods of molecular design for the cultivation of breeding super rice in ideal plant types.
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