Huanglongbing (HLB), also known as citrus greening, is the most severe pandemics in citrus in more than 50 countries in Asia, Africa, and America, causing serious economic losses worldwide (Gottwald,2020 2020; Wang, 2019). The disease is associated with a phloem-limited and fastidious member of the α-proteobacteriacea. 'Candidatus Liberibacter asiaticus' (CLas) is the most prevalent strain. It was frequently detected in leaves, stems, and roots based on PCR detection, which recognized both living and dead cells. Yet only intact and viable CLas cells are potentially infectious and transmissible. Previous study showed 17 to 31% of CLas cells were considered viable in HLB symptomatic tissues (Trivedi et al., 2009). Whether viable CLas is present in floral organs remains unclear and the possibility that the embryo could be infected via pollen has not yet been addressed. In this study, we aimed to identify viable CLas in citrus floral parts and the possibility of the dissemination through pollination process with anti-OmpA and anti-SDE1, two highly specific antibodies against CLas (Ding et al., 2020; Tran et al., 2020). These results will deepen our knowledge of the distribution in planta and the new dissemination pathway of CLas, which is important for the monitoring of HLB. The study was carried out with 1113 samples of 5 citrus varieties collected in China. CLas DNA was detected in anther filament, pollen grains, stigma, ovary, and receptacle (Figure 1A). Significant differences were observed among the detection ratio in different floral organs (P < 0.05). Direct tissue blot immuno assay (DTBIA) revealed purple colour in the tissues from CLas-infected stigmas, ovary, locules, and receptacle (Figure 1B). And in developing anthers, pollen grains, and the germinated pollen tubes (Figure 1C). We expected that the invasion of viable CLas into floral parts would follow the same as the invasion of branch buds. Unpollinated lemon flower buds were tested. CLas was located in the phloem of both the branch and flower bud, especially in the joint connection between the receptacle and flower branch (Figure 1D). Therefore, the early infection of flower buds was originated from the mother plant through phloem connections. To find out the possibility of CLas dissemination from stigma to ovary, artificial cross-pollination was performed (Figure 1F). In paternal pollens, signals were observed inside the pollen grains in the locules as well as in the vascular bundles. After cross-pollination, CLas were firstly detected on the stigma in 4 hpp, and then moved from stigma to stylet via pollen tubes. In 3 dpp, CLas was found in the ovary and mainly localized in the ovary wall, as well as in locules. These results coincided with PCR (Figure 1E) and were consistent with the germination rate of CLas-affected pollen tubes observed by fluorescence microscopy (Figure 1G). Our results showed the dissemination of CLas from stigma to ovary through pollination process. In this study, the presence of viable CLas in the pollen itself, especially in the pollen tube, opens the possibility that infection of the embryo could occur from the pollen and thus avoid the chalazal barrier. Based on our data, the distribution of CLas within an infected flower and a pathway for the potential infection of the ovary of a healthy flower can be summarized (Figure 1H). It is worth noting that seedlings grew out from CLas-affected fertile seeds indicated the existence of the bacteria in extreme low titre and became undetectable in the late stage (data not shown). We suggest that the aborted seed may be the result of infection of the embryo via pollination, whereas the viable seed with contaminated seed coats or rarely embryo are largely due to the infection from the maternal plant. The low title of CLas infection failed to sustain itself as the seedlings grew, suggesting that the CLas populations being transmitted to the seedling either not existed in a viable form or missed some of the populations necessary for multiplication and virulence. In conclusion, viable CLas was firstly identified in citrus floral organs, especially in pollen and pollen tubes. The distribution of CLas in pollen grains and pollen tubes opened a new possible dissemination pathway through pollination which should be also taken into account for the integrated control of HLB. This study was supported by the Science and Technology Major Project of Guangxi (Gui Ke AA18118046), the National Natural Science Foundation of China (31872077), the National Key Research & Development Program of China (2018YFD0201500), and the Fundamental Research Funds for the Central Universities (2662016PY099). The authors declare no competing interests. Q.L. Wang, Y.L. Xu, and X.F. Yang initiated the study, and contributed equally; J. Jia, J.L. Zhou, J.W. Zeng, X. Yan, J.X. Li, J.Q Yue, J. Guo, Y. Yang, C.X. Xia contributed samples and data analysis. N. Hong, G.P. Wang, S.A. Peng, Y.P. Duan, J.S. Hartung, and F. Ding contributed to critically revising of the manuscript.
Abstract Leaf morphology is one of the most important features of the ideal plant architecture. However, the genetic and molecular mechanisms controlling leaf morphology in crops remain largely unknown, despite their central importance. Here we demonstrate that the APC/C TAD1 -WL1-NAL1 pathway regulates leaf width in rice, and mutation of WL1 leads to width leaf variation. WL1 interacts with TAD1 and is degraded by APC/C TAD1 , with the loss of TAD1 function resulting in narrow leaves. The WL1 protein directly binds to the regulatory region of NAL1 and recruits the corepressor TOPLESS-RELATED PROTEIN to inhibit NAL1 expression by down-regulating the level of histone acetylation of chromatin. Furthermore, biochemical and genetic analyses revealed that TAD1, WL1, and NAL1 function in a common pathway to control leaf width. Our study establishes an important framework for the APC/C TAD1 -WL1-NAL1 pathway-mediated control of leaf width in rice and introduces novel perspectives for using this regulatory pathway for improving crop plant architecture.
Main component analysis and cluster analysis are performed by using 15 physical and chemical indexes of 12 soil profiles in Guanzhong Area. The results indicate that the contribution rate of the first four principal components was 86.41%.The 12 profiles were grouped into 3 types when threshold equal to 4.0(T=4.0).Obvious difference exists in the different groups, whereas the characteristics were similar in the same group. By comparing the numerical value taxonomy and soil taxonomy, it shows that the classification results were basically the same, except the individuals showing relatively huge difference. It is practicable that the numerical value taxonomy applies on soil classification in Guanzhong Area.
Abstract Leaf morphology is one of the most important features of the ideal plant architecture. However, the genetic and molecular mechanisms controlling this feature in crops remain largely unknown. Here, we characterized the rice (Oryza sativa) wide leaf 1 (wl1) mutant, which has wider leaves than the wild-type due to more vascular bundles and greater distance between small vascular bundles. WL1 encodes a Cys-2/His-2-type zinc finger protein that interacts with Tillering and Dwarf 1 (TAD1), a co-activator of the anaphase-promoting complex/cyclosome (APC/C) (a multi-subunit E3 ligase). The APC/CTAD1 complex degrades WL1 via the ubiquitin-26S proteasome degradation pathway. Loss-of-function of TAD1 resulted in plants with narrow leaves due to reduced vascular bundle numbers and distance between the small vascular bundles. Interestingly, we found that WL1 negatively regulated the expression of a narrow leaf gene, NARROW LEAF 1 (NAL1), by recruiting the co-repressor TOPLESS-RELATED PROTEIN and directly binding to the NAL1 regulatory region to inhibit its expression by reducing the chromatin histone acetylation. Furthermore, biochemical and genetic analyses revealed that TAD1, WL1, and NAL1 operated in a common pathway to control the leaf width. Our study establishes an important framework for understanding the APC/CTAD1–WL1–NAL1 pathway-mediated control of leaf width in rice, and provides insights for improving crop plant architecture.
Each layer of super high tower body is outwards protuberant, scaffoldding cantilevered end larger. This paper analyzes and researches the ultra-high tower overhanging scaffolding construction preparation, high scaffold material requirements, construction requirements, scaffold erection and dismantling construction technology and other aspects, it solves the high difficulty in construction, and provides practical basis and construction experience for super high steel tower mast structure.
Seasonal changes in nutrient concentrations of leaf and fruit structural parts (rind and pulp) from ‘Newhall’ (Citrus. sinensis Osbeck) and ‘Skagg's Bonanza’ (C. sinensis Osbeck) navel oranges were investigated during fruit development in two successive years. Leaf calcium (Ca), manganese (Mn), and potassium (K) concentrations were relatively constant throughout the whole season with the exception of an increase of K at stage 1, the period of fruitlet growth [before 80 days after full bloom (DAFB)], whereas the magnesium (Mg), boron (B), iron (Fe), and zinc (Zn) concentrations declined distinctly during stage 2 (80–180 DAFB), the period of fruit rapid enlargement. In rind, Ca, B, Fe, and Mn concentrations reached the greatest levels at stage 2, different from K and Mg, which increased at stage 1 and decreased thereafter. In pulp, concentrations of Ca, K, Mg, and Mn declined gradually with time, whereas a small rise in B toward the end of sampling and a clear increase of Fe at stage 2 were observed. It was suggested that ‘Newhall’ required greater B inherently in fruits as the cultivar had greater B concentrations in fruit parts and had greater rind/leaf B concentration ratios than ‘Skagg's Bonanza.’ ‘Newhall’ had relatively greater rind Ca content and exhibited Ca distribution more uniformly within its fruit parts, which probably enhanced the crack resistance.
Abstract Huanglongbing (HLB) is the most devastating citrus disease worldwide. The organism associated with the disease is spread by an insect vector, Diaphorina citri , commonly known as Asian citrus psyllid (ACP). Current management of HLB relies either on physical removal of the infected plants or on chemical control of ACP. Both methods are costly and not overly effective. In addition, public concerns regarding insecticide residues in fruit have greatly increased in recent years. It has been hypothesized that plant volatiles could act as repellents to ACP, thus reduce the incidence of HLB. To test this hypothesis, the repellency of fresh tissues of 41 aromatic plant species to ACP was investigated. The repellency of individual species was determined using a Y‐tube olfactometer. Our results showed that volatiles of five plant species were highly effective in repelling ACP with repellency as much as 76%. Among these, the tree species, Camptotheca acuminate , a nd the two shrubs, Lantana camara and Mimosa bimucronata , could potentially be planted as a landscape barrier. The two herbs, Capsicum annuum and Gynura bicolor , could potentially be used as interplantings in orchards. This is the first time that the repellency of fresh tissues from a diverse range of plant species to ACP has been determined. Although further field evaluation of various interplanting regimes and landscape barriers are needed to assess their effectiveness, our results showed that these aromatic species, being highly repellent to ACP, offer great potential as more cost‐effective and environmentally sustainable alternatives to the current methods of managing HLB.
Dynamic analysis models of two adjacent transmission towers, two adjacent corner towers and the correspond single-tower are established, its dynamic characteristics are analyzed and compared. The results showed that: Dynamic characteristics of two adjacent transmission towers are close, but the towers connected with the corner tower changes much. Compared with the single-tower, its dynamic characteristics have changed regardless of corner tower or straight line transmission towers. It is also shown that suspended cables not only have mass effects, but have coupled stiffness effects applied to towers on transverse direction and longitudinal direction.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)