Plant, Cell & Environment最新文献

Legumes have the beneficial capacity to establish symbiotic interactions with rhizobia, which provide their host plants with fixed nitrogen. However, in the presence of nitrogen, this process is rapidly repressed to avoid unnecessary investments of carbon in the symbiosis. Several players involved in regulating nodulation in response to nitrate availability have been identified, including peptide hormones, microRNAs and transcription factors. Nevertheless, how these molecular players are linked to each other and what underlying molecular mechanisms are at play to inhibit nodulation remain unresolved. Nitrate-mediated control of nodulation seems to differ between model legumes, such as Medicago and Lotus, compared to legume crops such as soybean. A deeper understanding of these regulatory processes, particularly in soybean, is expected to contribute to establishing increased nodulation efficiency in modern agricultural systems, hence improving sustainability by reducing the need for environmentally hazardous nitrogen fertilizers. This review describes the state of the art of nitrate-regulated nodulation in soybean, while drawing parallels with molecular mechanisms described in other legumes and addressing knowledge gaps that require future study.

Mineral deficiency is a major problem in agriculture. Plant adaption to low mineral environments involves signaling between shoots and roots, via the food transport cells, the sieve elements. However, due to the sequestered position of the sieve elements in the vascular bundles, identifying shoot-to-root mobile signals is challenging. In herbaceous species, sieve elements and companion cells (CCs) are isolated from other leaf tissues. We hypothesize that phloem CCs play an essential role by synthesizing shoot-to-root signals in response to mineral deficiency. To test this hypothesis, we analyzed gene expression responses in Arabidopsis CCs under phosphorus deficiency using TRAP-Seq. Phosphorus was chosen for its importance in plant growth and the known role of shoot-to-root signaling in regulating root phosphate transporters during deficiency. Our findings revealed that CCs exhibit more dramatic molecular responses than other leaf cells. We also found that many genes altered in CCs have potential functions in regulating root growth. This is unexpected because it has been widely believed that shoot-to-root signaling is not involved in root growth regulation under P deficiency. The importance of CCs in regulating mineral deficiency may extend beyond phosphorus because shoot-to-root signaling is a common response to the deficiency of various minerals.

Plant-microbe interactions have been studied extensively in legumes, but the influence of host developmental stages on its microbiome remains poorly understood. The rhizospheric region enriched with microbial diversity presents an optimal environment to investigate this relationship. We employed a multi-omics meta-analysis approach to identify the rhizospheric bacteria co-existing with legumes at different developmental stages. The data from eight different legume species across various geographical locations, soil conditions and developmental stages (vegetative, reproductive and maturation) were included in the study. A total of 10 developmental stage-specific marker bacteria were identified and found to be positively associated with plant growth phenotypes. The functional profiling elucidated the expression of these marker bacterial genes, indicating the active presence of marker bacteria. Co-expression network analysis revealed the involvement of gene clusters in biological processes such as cobalt and nitrogen metabolism. Further, pathway enrichment analysis illustrated the role of these bacteria in plant metabolic pathways, such as biosynthesis of various plant secondary metabolites, biotin metabolism and carbon fixation in photosynthetic organisms. Our study identified a positive relationship between marker bacteria and the host plant, suggesting their crucial role in legume growth and development that could further aid in crop improvement strategies.

Black rot caused by hemibiotrophic Xanthomonas campestris pv. campestris (Xcc) is a great problem in crucifer crop production. Various host responses are activated upon Xcc attack; however, their roles in black rot resistance remain ambiguous. In this study, a highly black rot resistance of host plants was achieved by applying a field-screened systemic resistance-eliciting Bacillus velezensis strain 37-1. The contributions of strain 37-1-altered host responses to Xcc resistance were then investigated in Arabidopsis. Hypersensitive response and hydrogen peroxide accumulation were demonstrated beneficial for Xcc infection by using nrg1 and rbohd mutants, histochemical staining against host cell death and reactive oxygen species, detection of antioxidant enzyme activity and RT-qPCR assay. By contrast, salicylic acid was proven essential for black rot suppression by using NahG transformant, mutants impaired in defence hormone synthesis and signalling pathway, and RT-qPCR assay. Additionally, both isochorismate synthase and phenylalanine ammonia-lyase pathways for salicylic acid biosynthesis were found to be involved in resistance to Xcc. These findings improve the knowledge of host defence responses crucial for fighting off hemibiotrophic Xcc.

Cowpea (Vigna unguiculata) is an important protein source in Sub-Saharan Africa. Optimizing resilience and productivity through genetic engineering in cowpea has been slow due in part to a lack of defined species-specific regulatory elements and difficulty testing gene function within the native system. In many plant species, Agrobacterium-mediated transient gene expression is widely used to validate constructs before investing in transgenic lines, but its implementation in legumes has been challenging. In this study, we optimized an in planta agroinfiltration assay in trifoliate cowpea leaves using a betalain reporter. To demonstrate the "intact plant" aspect of this system, we used this assay to characterize drought-inducible promoters by challenging cowpea plants with drought stress. Subsequently, to identify and broaden the pool of native promoters known in cowpea, we developed a user-friendly web application, CowPEAsy, allowing users to interrogate gene expression from our canopy-level, developmental-series RNA-Seq data set. Finally, using CowPEAsy, we identified six promoters that showed constitutive expression across all conditions and verified these promoters with our transient system. This work provides an in vivo platform for preliminary validation of regulatory elements in cowpea and other legumes and enhances current genetic resources by identifying a suite of physiologically relevant promoters of varying strengths.

Brassica napus (canola) is a significant contributor to the world's oil production and is cultivated across continents, yet acidic soils with aluminium (Al³⁺) and manganese (Mn²⁺) toxicities limit its production. The genetic determinants underlying natural variation for acidic soil tolerance in canola are unknown and need to be determined. Through genome-wide association analysis of 326 canola accessions, we identified three QTLs for tolerance to Mn²⁺ toxicity on chromosomes A09, C03, and C09. Allelism tests between four tolerance sources confirmed that at least one locus on A09 controls Mn²⁺ tolerance in canola. Integrated analyses of genomic and expression QTL and Mn²⁺ tolerance data revealed that BnMTP8.A09, possibly in conjunction with BnMATE.C03, BnMTP8.C04 and BnMTP8.C08, play a central role in conferring Mn²⁺ tolerance in canola. Gene expression analysis showed that variation in BnMTP8.A09 expression could account for upto 74% of the variation in Mn²⁺ tolerance between individuals with extreme phenotypes. Yeast complementation assays and ectopic expression in Arabidopsis show that BnMTP8.A09 can complement manganese-hypersensitive yeast mutant strain PMR1∆ and Arabidopsis atmtp8 mutant background, respectively and restore Mn²⁺ tolerance to wild-type levels. Our multi-omics research approach unveils the genetic architecture of Mn²⁺ tolerance and identifies BnMTP8.A09 as a causal gene imparting tolerance to Mn²⁺ toxicity in canola.

The survival time of trees under drought is intimately linked to leaf minimum water conductance on the leaf surface (g_min), which determines the residual water loss of trees after maximum stomatal closure. Considerable interspecies variation of g_min in trees has been documented, but intraspecific variation resulting from genetic variation (G) and phenotypic plasticity (E) remains unclear. We measured the temperature response (T) of g_min in different provenances of four temperate tree species growing in three common gardens differing in water availability and assessed G, E and G × E of g_min and T. Additionally, we explored how leaf cuticular and stomatal traits are related to the intraspecific variation of g_min. For all species, our results showed strong T, low G and high E for g_min. Interestingly, E was more pronounced in deciduous angiosperm trees than in evergreen conifers. Surprisingly, there was significant E × T in some species. Contrary to our expectation, we found no significant effect of leaf stomatal and cuticular traits on g_min. Our study suggests that E is the most potent driver of intraspecies variation of g_min, possibly contributing to the acclimation of deciduous trees to a future hotter and dryer climate.

Catalpa bungei is a highly valued timber species renowned for its superior wood properties. However, the development of tension wood (TW) induced by wind and other mechanical stresses during the growing season significantly reduces its economic value. Although Homeodomain Leucine Zipper (HD-Zip), a plant-specific transcription factor family, has been reported to play various roles in plant growth, development, and stress resistance, a systematic characterisation of the HD-Zip gene family in C. bungei, particularly regarding the regulatory mechanisms involved in TW formation, is still lacking. Here, we identified a total of 48 HD-Zip genes (Cbuhdzs) in C. bungei and analysed their phylogeny, structure, and expression profiles. In particular, Cbuhdz34, a member of the HD-Zip I subfamily, was specifically upregulated during TW formation. To further explore its function, we overexpressed Cbuhdz34 (OE-Cbuhdz34) in poplar '84 K', which led to noticeable changes in plant growth and fibre cell length. Moreover, compared with wild-type plants, the OE-Cbuhdz34 plants presented increased TW formation under bending stress, as indicated by increased TW width, gelatinous layer width, and eccentric growth rate, suggesting a positive regulatory role in TW formation. Additionally, hierarchical genetic regulatory network analysis revealed the direct targets of Cbuhdz34, including CbuMYB63 and three genes involved in cell wall synthesis (CbuGATL1, CbuFLA17, and CbuLRR14). Further, yeast one-hybrid and dual-luciferase reporter assays confirmed the activation of these targets by Cbuhdz34. In conclusion, our results provide insights into the molecular mechanisms by which Cbuhdz34 regulates TW formation and lay a genetic foundation for the potential improvement of wood quality in C. bungei.

Leaf morphology is crucial for plant photosynthesis and stress adaptation. While CIN-like TCP transcription factors are well-known for their roles in leaf curling and morphogenesis, the function of CYC-like TCPs in leaf development remains largely unexplored. This study identifies CmCYC2d as a key regulator of abaxial leaf curling in Chrysanthemum morifolium. Phenotypic analysis revealed that the downward curling observed in OX-CmCYC2d transgenic lines was primarily due to the enlargement of adaxial epidermal cells. Furthermore, a reduction in epidermal cell number was identified as a significant contributor to the smaller leaf area in these plants. Transcriptome and WGCNA analyses highlighted CmSAUR55 as a potential downstream target of CmCYC2d. ChIP-qPCR, EMSA, and LUC assays confirmed that CmCYC2d directly bound to the CmSAUR55 promoter. Additionally, transcriptome data revealed that the reduced cell number in OX-CmCYC2d transgenic lines may be mediated by auxin-related pathways and key genes such as CNR7. The CmCYC2d-CmSAUR55 module was also closely linked to the development of enlarged adaxial epidermal cells in the leaf sinus, emphasising its role in this developmental process. This study highlights the regulatory role of CmCYC2d in leaf development and sheds light on the molecular mechanisms underlying leaf curling in chrysanthemum.