Plant Cell Reports最新文献

Key message: NnNAC100-NnSBEII modules enhance starch content of the rhizome in Nelumbo nucifera Gaertn. Nelumbo nucifera Gaertn. is a popular aquatic vegetable and traditional Chinese medicine whose quality and taste are mainly determined by the starch. Although starch-related genes have been functionally characterized, the regulated mechanism of enzyme (SBE) remains unclear. In this study, we identified and functionally elucidated the functions of NnSBEII and NnNAC100 using transient overexpression of NnSBEII and NnNAC100 in rhizomes of lotus, and it significantly increased the amylopectin content and total starch content. Accordingly, functional complementation assay in defective Arabidopsis also showed that NnSBEII compensated for the low content of starch in the mutant sbe2.2. In addition, overexpression of NnSBEII and NnNAC100 significantly increased the content of starch in transgenic lines. Consistently, opposite results were observed under the background of repressed NnSBEII and NnNAC100 in rhizomes of lotus. Furthermore, yeast one-hybrid and dual-luciferase assays revealed that NnNAC100 could directly bind to the NnSBEII promoter and promote the expression of NnSBEII. Transient overexpression of NnNAC100 upregulated NnSBEII expression significantly, while the expression level of AtSBE2.2 in transgenic Arabidopsis overexpressing NnNAC100 was higher than that of WT, which indicated that NnNAC100 promoted the synthesis of amylopectin by enhancing the expression of NnSBEII. In addition, we found that NnSBEII could form a complex protein by interacting with soluble starch synthase (NnSS2) to increase the activity of the SBEII enzyme. These results reveal a novel mechanism that the NnNAC100-NnSBEII-NnSBEII/NnSS2 module regulates amylopectin biosynthesis and these will provide insights into the broader implications of the regulation mechanism of starch biosynthesis.

Key message: Auxin stimulates chloroplast division by upregulating the expression of genes involved in chloroplast division and influencing the positioning of chloroplast division rings. Chloroplasts divide by binary fission, forming a ring complex at the division site. Auxin, particularly indole acetic acid (IAA), significantly influences various aspects of plant growth. However, the impact of auxin on chloroplast division remains unclear. In this study, different concentrations of exogenous IAA were applied to wild Arabidopsis thaliana. The results showed that the number and size differences of chloroplasts in the cells of Arabidopsis thaliana treated with high concentrations of IAA increased compared to untreated plants. Further investigation revealed that high concentrations of IAA affected the expression of chloroplast division genes and the formation of division rings. In chloroplast division mutants, the effect of IAA on promoting chloroplast division is impaired. Defects of IAA synthetic gene also lead to a reduced effect of IAA on chloroplast division. Our findings demonstrate that auxin influences chloroplast division by regulating the expressions of chloroplast division genes and affecting the localization of division rings. These results are significant for further exploring the relationship between auxin and chloroplast division.

Key message: Everlastin1 and Everlastin2, potent inhibitors of EPH1, were identified through a wheat cell-free chemical-screening system. This innovative platform enables the development of small molecules that target 'undruggable' transcription factors. By specifically targeting the EPH1 pathway, these inhibitors delay petal senescence, extending the longevity and quality of ornamental flowers. This approach offers a precise alternative to traditional postharvest treatments. Moreover, this chemical discovery strategy can be applied to develop inhibitors for other agriculturally important traits and disease-related transcription factors, opening up broad applications in floriculture, agriculture, and beyond.

Key message: We characterized the WAK gene family in Gossypium barbadense and revealed the potential function of GbWAK5 in regulating salt tolerance by modulating ion homeostasis. Soil salinization is one of the main factors restricting cotton production. Although the role of the wall-associated kinases (WAKs) in plants has been extensively studied, its response to salt stress in sea-island cotton (Gossypium barbadense L.) has not been reported. Here, we conducted a whole-genome analysis of the WAK gene family in G. barbadense, identifying a total of 70 GbWAK genes, which were classified into five clades. Segmental and tandem duplication events have contributed to the expansion of the GbWAK gene family. A large number of cis-acting elements were predicted in the GbWAK promoter region. Through RNA sequencing, 37 GbWAKs that potentially play a role in cotton's response to salt stress were screened out, among which 10 genes with sustained up-regulated expression were confirmed by quantitative real-time PCR (qRT-PCR). GbWAK5, a member of Clade II, was significantly up-regulated following NaCl treatment and exhibited a typical WAK structure. Subcellular localization indicated that GbWAK5 is localized on the plasma membrane. Virus-induced gene silencing (VIGS) experiments revealed that the knockdown of GbWAK5 resulted in more severe dehydration and wilting in plants compared to the control under NaCl treatment. RNA-seq analysis revealed that several ion transport-related genes were down-regulated in TRV:GbWAK5 plants under salt stress, while TRV:GbWAK5 plants accumulated more Na⁺ and exhibited a higher Na⁺/K⁺ ratio compared to TRV:00 plants. These results offer a comprehensive analysis of the G. barbadense WAK gene family for the first time, and conclude that GbWAK5 is a promising gene for improving cotton's resistance to salt stress.

Key message: Plant extracellular vesicles play a role in systemic acquired resistance by facilitating the transmission of immune signals between plant cells. Extracellular vesicles (EVs) play a critical role in facilitating the transfer of nucleic acids and proteins between plants and pathogens. However, the involvement of plant EVs in intercellular communication and their contribution to the regulation of physiological and pathological conditions in plants remains unclear. In this study, we isolated EVs from the apoplast of Arabidopsis plants induced by systemic acquired resistance (SAR) and conducted proteomic and physiological analyses to investigate the role of EVs in SAR. The results demonstrated that plant cells are capable of internalizing EVs, and EV secretion was enhanced in SAR-induced plants. EVs isolated from SAR-induced plants effectively inhibited the spore production of Botrytis cinerea, activated the transcription of several SAR marker genes, and improved plant resistance to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). Several proteins associated with defense responses were enriched in EVs upon SAR induction. Among these, the receptor-like kinase H₂O₂-Induced Ca²⁺ Increase 1 (HPCA1) was identified as a crucial component in SAR. In addition, plant EVs contained numerous proteins involved in the transmission of signals related to pathogen-associated molecular patterns-triggered immunity (PTI) and effector-triggered immunity (ETI). Our findings suggest that plant EVs are functionally involved in the propagation of SAR signals and may play diverse roles in plant immune responses.

Key message: Transcription factor OsGRAS2 regulates salt stress tolerance and yield in rice. Plant-specific GRAS transcription factors are involved in many different aspects of plant growth and development, as well as in biotic and abiotic stress responses, although whether and how they participate in salt stress tolerance in rice (Oryza sativa) remains unclear. A screen of a previously generated set of activation-tagged lines revealed that Activation Tagging Line 63 (AC63) displayed a salt stress-sensitive phenotype. Subsequent thermal asymmetric interlace polymerase chain reaction (TAIL-PCR) showed that AC63 was due to overexpression of OsGRAS2. Ectopic overexpression of OsGRAS2 caused increased salt stress sensitivity, while osgras2 loss-of-function lines displayed salt stress-resistant phenotypes. Further, we observed that OsGRAS2 impacts Na⁺ and K⁺ ion homeostasis in the shoots. Mutation of OsGRAS2 increased salt tolerance without yield penalty. Phylogenetic tree analysis indicated that OsGRAS2 belonged to the LISCL subfamily of GRAS transcription factors and had high amino acid similarity to OsGRAS23. Both OsGRAS2 and OsGRAS23 underwent homomeric and heteromeric interactions, indicating that they formed homo- and hetero-dimers. Moreover, OsGRAS2 and OsGRAS23 showed transcriptional activation activity that was mostly governed by motif1, which was located at the N-terminal region. Further, we found OsGRAS2 binds to the OsWRKY53 promoter to increase its expression, thereby negatively impacting the OsHKT1;5 expression. This study demonstrates a novel insight into how LISCL subfamily GRAS transcription factors impact salt stress tolerance in rice.

Key message: CesA proteins response to arsenic stress in rice involves structural and regulatory mechanisms, highlighting the role of BES1/BZR1 transcript levels under arsenate exposure and significant downregulation of BZR1 protein expression. Plants interact with several hazardous metalloids during their life cycle through root and soil connection. One such metalloid, is arsenic and its perilous impact on rice cultivation is a well-known threat. Cellulose synthase and cellulose synthase-like (CesA/CSL) gene family build major constituent of cell wall polysaccharides, however, their interaction and responses to arsenic stress remains enigmatic. The current study describes the structural, functional, and regulatory behavior of CesA proteins using in silico tools with datasets of 367 sequences and an in vitro germination model. Interpro analysis revealed six types of domains, further classified into two major clades: cellulose synthase and glycosyl transferase family group 2 exhibiting polyphyletic grouping. The MEME suite analysis identified the frequent occurrence of "QXXRW" among 35 identified conserved motifs. Further observation of the regulatory mechanism of CesA identified 36 types of trans-regulatory elements involved in hormone signaling, developmental regulation, stress response, etc. Among these, hormone signaling comprises of 7 types of elements, with BES1 being less studied, sequences containing BES1 sites were selected. Additionally, 56 cis-regulatory elements were identified. Arsenate exposure increased transcript level of CesA and BES1/BZR1 compared to control. Western blot analysis revealed a significant downregulation of the BZR1 protein expression in arsenate stressed seedlings. This research shed light on the regulation of CesA mediated by (BES1/BZR1) and brassinosteroid signalling.

In the past decade, there has been an emerging gap between the demand and supply of vegetable oils globally for both edible and industrial use. Lipids are important biomolecules with enormous applications in the industrial sector and a major source of energy for animals and plants. Hence, to elevate the lipid content through metabolic engineering, new strategies have come up for triacylglycerol (TAG) accumulation and in raising the lipid or oil yield in crop plants. Increased levels of energy density can be achieved by single and multiple gene strategies that re-orient the carbon flux into TAG. Transcription factors and enzymes of the metabolic pathways have been targeted to foster lipid production. Oleosin, a structural protein of the lipid droplet plays a vital role in its stabilization and subsequently in its mobilization for seed germination and seedling growth. Maintenance of increased lipid content with optimal composition is a major target. Knowledge gained from genetic engineering strategies suggests that oleosin co-expression can result in a significant shift in carbon allocation to LDs. In this review, we present a detailed analysis of the recent advancements in metabolic engineering of plant lipids with emphasis on oleosin with its distinct patterns and functions in plants.

Key message: OsMYB1 negatively mediates rice resistance to brown planthopper and rice blight. Additionally, OsMYB1 interacts with OsSPL14 and antagonizes its function by oppositely regulating downstream resistance-related genes. In their natural habitats, plants are concurrently attacked by different biotic factors. Xanthomonas oryzae pv. oryzae (Xoo) is a pathogen that severely deteriorates rice yield and quality, and brown planthopper (BPH; Nilaparvata lugens) is a rice specific insect pest with the damage topping other pathogens. Although genes for respective resistance to BPH and Xoo have been widely reported, few studies pay attention to simultaneous resistance to both. In this study, we identified a MYB transcription factor, OsMYB1, which exhibited diverse transcriptional regulatory capabilities and a negative regulatory role in resistance to both BPH and Xoo. Biochemical and genetic analysis proved OsMYB1 to be a TF that could interact with OsSPL14, a positive regulator of rice resistance to Xoo. OsSPL14 mutants showed increased sensitivity to BPH, suggesting that OsSPL14 is contrary to OsMYB1 in regulating rice resistance to these two biotic stresses. Consistently, OsMYB1 and OsSPL14 displayed opposite functions in regulating defense-related genes. OsMYB1 can form transcription regulation complexes with repressor OsJAZs instead of co-repressor TOPLESS to possibly realize its transcriptional repression function. Taken together, we concluded that two interacting TFs in rice, OsMYB1 and OsSPL14, played antagonistic roles in regulating resistance to BPH and Xoo.

Chloroplasts, distinctive subcellular organelles found exclusively in plant species, contain three membranes: the outer, inner, and thylakoid membranes. They also have three soluble compartments: the intermembrane space, stroma, and thylakoid lumen. Accordingly, delicate sorting mechanisms are required to ensure proper protein targeting to these sub-chloroplast compartments. Except for most outer membrane proteins, chloroplast interior proteins possess N-terminal cleavable transit peptides as primary import signals. After the cleavage of transit peptides, which occurs during or after import into chloroplasts, the inner and thylakoid membrane proteins, as well as stromal and thylakoid luminal proteins, are further sorted based on additional targeting signals. In this review, we aim to recapitulate the mechanisms by which proteins are targeted to chloroplasts and subsequently sorted into sub-chloroplast compartments, with a focus on the design principles of sorting signals present in chloroplast proteins.