Allelic variation in the Arabidopsis TNL CHS3/CSA1 immune receptor pair reveals two functional cell-death regulatory modes
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Some plant NLR immune receptors are encoded in head-to-head "sensor-executor" pairs that function together. Alleles of the NLR pair CHS3/CSA1 form three clades. The clade 1 sensor CHS3 contains an integrated domain (ID) with homology to regulatory domains, which is lacking in clades 2 and 3. In this study, we defined two cell-death regulatory modes for CHS3/CSA1 pairs. One is mediated by ID domain on clade 1 CHS3, and the other relies on CHS3/CSA1 pairs from all clades detecting perturbation of an associated pattern-recognition receptor (PRR) co-receptor. Our data support the hypothesis that an ancestral Arabidopsis CHS3/CSA1 pair gained a second recognition specificity and regulatory mechanism through ID acquisition while retaining its original specificity as a "guard" against PRR co-receptor perturbation. This likely comes with a cost, since both ID and non-ID alleles of the pair persist in diverse Arabidopsis populations through balancing selection.Keywords:
Immune receptor
Homology
Dark-grown transgenic Arabidopsis seedlings expressing the C-terminal domains (CCT) of the cryptochrome (CRY) blue light photoreceptors exhibit features that are normally associated only with light-grown seedlings, indicating that the signaling mechanism of Arabidopsis CRY is mediated through CCT. The phenotypic properties mediated by CCT are remarkably similar to those of the constitutive photomorphogenic1 (cop1) mutants. Here we show that Arabidopsis cryptochrome 1 (CRY1) and its C-terminal domain (CCT1) interacted strongly with the COP1 protein. Coimmunoprecipitation studies showed that CRY1 was bound to COP1 in extracts from both dark- and light-grown Arabidopsis. An interaction also was observed between the C-terminal domain of Arabidopsis phytochrome B and COP1, suggesting that phytochrome signaling also proceeds, at least in part, through direct interaction with COP1. These findings give new insight into the initial step in light signaling in Arabidopsis, providing a molecular link between the blue light receptor, CRY1, and COP1, a negative regulator of photomorphogenesis.
Photomorphogenesis
Phytochrome
Immunoprecipitation
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Thellungiella salsuginea (先前 T。halophila ) ，种仔细与 Arabidopsis (Arabidopsis thaliana ) 有关，是容忍的不仅高腌层次，而且到寒心，结冰，并且臭氧。这里，我们报导那 T。salsuginea 也比 Arabidopsis 显示出更大的热忍耐。我们识别了 T。作为基因，那能授与的 salsuginea HsfA1d (TsHsfA1d ) 在 Arabidopsis 上标记热忍耐。TsHsfA1d 经由全身的 cDNA 被识别从许多 heat-stress-related T 之中狩猎的过去表示的基因(狐狸) 。salsuginea cDNAs。转基因的 Arabidopsis overexpressing TsHsfA1d 在正常生长温度下面在 Arabidopsis AtHsfA1 regulon 显示出许多基因的组成的起来规定。在 Arabidopsis 叶肉原物， TsHsfA1d 在原子核和细胞质是局部性的。TsHsfA1d 也与 AtHSP90 交往了，它否定地由在细胞质形成 HsfA1HSP90 建筑群调整 AtHsfA1s。TsHsfA1d 的部分原子本地化在正常温度在转基因的植物导致了 AtHsfA1d regulon 的表示，是可能的。我们也发现转基因的 Arabidopsis 植物 overexpressing AtHsfA1d 比野类型的植物更热容忍、起来调整 HsfA1d regulon 的表示在 TsHsfA1d-overexpressing 植物被观察。我们建议 TsHsfA1d 和 AtHsfA1d 的产品作为 Arabidopsis 热压力反应的积极管理者工作并且将为在另外的植物的热压力忍耐的改进有用。
Regulon
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Arabidopsis has been popular as a model plant system for decades. Completion of the Arabidopsis genome and the availability of large expressed sequence-tag collections from other dicot species provides an opportunity to assess gene content in Arabidopsis , specifically by identifying genes from dicot test species that are absent from Arabidopsis . I report here results from these sorts of comparisons, carried out in part to assess the extent to which Arabidopsis is representative of dicot genomes and also the degree to which gene loss and novel gene acquisition has accompanied angiosperm speciation. More than 10% of the contigs from each of three dicot test species have no detectable homologue in Arabidopsis . By means of cross comparison among the test species, 154 specific cases of gene loss in the lineage leading to Arabidopsis were identified, including several well characterized enzymes and a group of proteins with strong homologs in the photosynthetic bacterium Synechocystis . These results show that although Arabidopsis is broadly representative of the other dicot genomes, there seems to be substantial variation even among relatively closely related genera. Further, although we cannot yet draw a causative link, variation in actual gene content seems appears to be a feature of angiosperm speciation.
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Pathogen perception by plants is mediated by plasma membrane-localized immune receptors that have varied extracellular domains. Lectin receptor kinases (LecRKs) are among these receptors and are subdivided into 3 classes, C-type LecRKs (C-LecRKs), L-type LecRKs (L-LecRKs) and G-type LecRKs (G-LecRKs). While C-LecRKs are represented by one or two members in all plant species investigated and have unknown functions, L-LecRKs have been characterized in a few plant species and have been shown to play roles in plant defense against pathogens. Whereas Arabidopsis G-LecRKs have been characterized, this family of LecRKs has not been studied in tomato.This investigation updates the current characterization of Arabidopsis G-LecRKs and characterizes the tomato G-LecRKs, using LecRKs from the monocot rice and the basal eudicot columbine to establish a basis for comparisons between the two core eudicots. Additionally, revisiting parameters established for Arabidopsis nomenclature for LecRKs is suggested for both Arabidopsis and tomato. Moreover, using phylogenetic analysis, we show the relationship among and between members of G-LecRKs from all three eudicot plant species. Furthermore, investigating presence of motifs in G-LecRKs we identified conserved motifs among members of G-LecRKs in tomato and Arabidopsis, with five present in at least 30 of the 38 Arabidopsis members and in at least 45 of the 73 tomato members.This work characterized tomato G-LecRKs and added members to the currently characterized Arabidopsis G-LecRKs. Additionally, protein sequence analysis showed an expansion of this family in tomato as compared to Arabidopsis, and the existence of conserved common motifs in the two plant species as well as conserved species-specific motifs.
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A phenotype-based screening of the T1 transgenic Arabidopsis population transformed by overexpression constructs of the entire poplar MYB transcription factor family found that overexpression of a poplar MYB transcription factor, PtrMYB012, in Arabidopsis resulted in upwardly curled rosette leaves, dwarfism and male sterility. Sequence analysis identified that PtrMYB012 is homologous to the Arabidopsis GAMYB genes (e.g., AtMYB65 and AtMYB33). Gene expression analysis revealed that PtrMYB012 is specifically expressed in floral tissues, especially in male catkins, similar to AtMYB65. It was well known that Arabidopsis GAMYBs are negatively regulated by microRNA159 (miR159) during vegetative growth; thus, the typical phenotypes of upwardly curled leaves, dwarfism and male sterility were only shown in overexpression of GAMYBs with mutations in the miR159 target sequence. To confirm our phenotypic consequences, we independently re-produced transgenic Arabidopsis plants overexpressing PtrMYB012 without mutations in the miR159 target sequence. The resulting 35 S::PtrMYB012 Arabidopsis plants phenocopied the previous transgenic Arabidopsis plants, suggesting that PtrMYB012 is probably not a target of Arabidopsis miR159 despite containing the conserved miR159 target sequence. To gain further insight, we produced transgenic poplars overexpressing the intact PtrMYB012. As a result, no conspicuous phenotype was found in 35 S::PtrMYB012 poplar plants. These results suggest that PtrMYB012 transcripts are down-regulated by miR159 in poplar but not in Arabidopsis. Indeed, subsequent 5'-RACE analysis confirmed that PtrMYB012 transcripts are completely degraded in poplar, probably by miR159, but not in Arabidopsis. These results suggest that species-specific family members of miR159 are important for the regulation of normal growth and development in plants.
MYB
Dwarfism
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GmSNAP18 and GmSHMT08 are two major genes conferring soybean cyst nematode (SCN) resistance in soybean. Overexpression of either of these two soybean genes would enhance the susceptibility of Arabidopsis to beet cyst nematode (BCN), while overexpression of either of their corresponding orthologs in Arabidopsis, AtSNAP2 and AtSHMT4, would suppress it. However, the mechanism by which these two pairs of orthologous genes boost or inhibit BCN susceptibility of Arabidopsis still remains elusive. In this study, Arabidopsis with simultaneously overexpressed GmSNAP18 and GmSHMT0 suppressed the growth of underground as well as above-ground parts of plants. Furthermore, Arabidopsis that simultaneously overexpressed GmSNAP18 and GmSHMT08 substantially stimulated BCN susceptibility and remarkably suppressed expression of AtPR1 in the salicylic acid signaling pathway. However, simultaneous overexpression of GmSNAP18 and GmSHMT08 did not impact the expression of AtJAR1 and AtHEL1 in the jasmonic acid and ethylene signaling pathways. GmSNAP18, GmSHMT08, and a pathogenesis-related (PR) protein, GmPR08-Bet VI, in soybean, and AtSNAP2, AtSHMT4, and AtPR1 in Arabidopsis could interact pair-wisely for mediating SCN and BCN resistance in soybean and Arabidopsis, respectively. Both AtSNAP2 and AtPR1 were localized on the plasma membrane, and AtSHMT4 was localized both on the plasma membrane and in the nucleus of cells. Nevertheless, after interactions, AtSNAP2 and AtPR1 could partially translocate into the cell nucleus. GmSNAP18 interacted with AtSHMT4, and GmSHMT4 interacted with AtSNAP2. However, neither GmSNAP18 nor GmSHMT08 interacted with AtPR1. Thus, no pairwise interactions among α-SNAPs, SHMTs, and AtPR1 occurred in Arabidopsis overexpressing either GmSNAP18 or GmSHMT08, or both of them. Transgenic Arabidopsis overexpressing either GmSNAP18 or GmSHMT08 substantially suppressed AtPR1 expression, while transgenic Arabidopsis overexpressing either AtSNAP2 or AtSHMT4 remarkably enhanced it. Taken together, no pairwise interactions of GmSNAP18, GmSHMT08, and AtPR1 with suppressed expression of AtPR1 enhanced BCN susceptibility in Arabidopsis. This study may provide a clue that nematode-resistant or -susceptible functions of plant genes likely depend on both hosts and nematode species.
Jasmonic acid
Soybean cyst nematode
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In Arabidopsis thaliana (Arabidopsis), nonhost resistance (NHR) is influenced by both leaf age and the moment of inoculation. While the circadian clock and photoperiod have been linked to the time-dependent regulation of NHR in Arabidopsis, the mechanism underlying leaf age-dependent NHR remains unclear. In this study, we investigated leaf age-dependent NHR to Pyricularia oryzae in Arabidopsis. Our findings revealed that this NHR type is regulated by both miR156-dependent and miR156-independent pathways. To identify the key players, we utilized rice-FOX Arabidopsis lines and identified the rice HD-Zip I OsHOX6 gene. Notably, OsHOX6 expression confers robust NHR to P. oryzae and Colletotrichum nymphaeae in Arabidopsis, with its effect being contingent upon leaf age. Moreover, we explored the role of AtHB7 and AtHB12, the Arabidopsis closest homologues of OsHOX6, by studying mutants and overexpressors in Arabidopsis-C. higginsianum interaction. AtHB7 and AtHB12 were found to contribute to both penetration resistance and post-penetration resistance to C. higginsianum in a leaf age- and time-dependent manner. These findings highlight the involvement of HD-Zip I AtHB7 and AtHB12, well-known regulators of development and abiotic stress responses, in biotic stress responses in Arabidopsis.
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To better understand the expression and function of the High Mobility Group Protein B(HMGB) family genes in Arabidopsis,we cloned the first five genes encoding HMGB proteins in Arabidopsis thaliana genome:AtHMGB1,AtHMGB2,AtHMGB3,AtHMGB4 and AtHMGB5.Real-time reverse transcription-PCR(RT-PCR) analysis was employed to determine the transcript levels of HMGB genes accurately in Arabidopsis wild-type under plant phytohormone treatment.Binary vectors carrying the AtHMGB2,AtHMGB4 and AtHMGB5 genes were transformed into Arabidopsis to detect the phenotype of the transgenic Arabidopsis induced by ABA.Our results proved that AtHMGB2 was more abundantly expressed than other family members,whereas AtHMGB4 and AtHMGB5 were more abundantly expressed in roots and flowers than in stems and leaves.The expression level of the AtHMGB family genes were markedly regulated by ABA induction,especially the AtHMGB2.Under ABA treatment,the transgenic Arabidopsis plants that over-expressed AtHMGB2 displayed retarded germination and subsequent growth compared with the wild-type Arabidopsis.Overexpression of AtHMGB4 and AtHMGB5 had little impact on seed germination and seedling growth of the plants by ABA induction.Taken together,these results provide a novel basis for understanding the biological functions of AtHMGB family members under ABA conditions.
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在 Arabidopsis 的南船座基因在控制植物机关尺寸起一个关键作用。决定它的功能是在米饭的 ortholog，从米饭纸巾的通常认为的南船座 orthologous 基因被孤立并且指定了为 OsARGOS。这基因在米饭染色体有仅仅一个拷贝。OsARGOS 抄本在大多数米饭纸巾被检测，特别地在年轻纸巾，并且它的表示被植物生长素或细胞激动素的申请在米饭幼苗导致。表示 OsARGOS 的 Arabidopsis 植物导致了更大的机关，例如叶子和 siliques，与野类型的植物相比。有趣地，根生长也在这些转基因的 Arabidopsis 植物被提高。因此，转基因的植物的生物资源显著地被增加。进一步的分析揭示了那，与在 Arabidopsis 的 ARGOS 和像南船座的基因不同， OsARGOS 基因由房间数字和房间尺寸的增加扩大了机关。另外，抄本调整细胞分割或细胞生长的联系尺寸的基因在上面的几个器官铺平在转基因的 Arabidopsis 植物调整了。我们也转了到米饭的 OsARGOS 基因，而是转基因的植物没与控制植物相比在机关尺寸显示出任何变化。在机关尺寸控制的 OsARGOS 的功能在米饭取决于另外的尺寸管理者，是可能的。在 Arabidopsis 的 OsARGOS 的表达式可以激活在植物生长和开发的功课期间控制房间增长和房间扩大的发信号的小径。自从 OsARGOS 原因机关增大的表示，通过遗传工程的这基因的潜在的申请可以显著地在农业实践改进生物资源的生产。
Silique
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