Journal of Experimental Botany最新文献

The inducer β-aminobutyric acid (BABA) participates in the immune response in various plants. However, the specific mitogen-activated protein kinase (MAPK) cascade involved in BABA-induced resistance (BABA-IR) has not yet been elucidated. Here, peach (Prunus persica) fruits treated with the BABA exhibited pattern-triggered immunity defense against Rhizopus stolonifer, accompanied by the generation of reactive oxygen species and activation of a MAPK cascade. Transcriptome sequencing suggested that a total of 15 MAPK kinase kinase (PpMAPKKK)/MAPK kinase (PpMAPKK)/PpMAPK genes were involved in BABA-IR in peach fruit. Further qRT-PCR analysis showed that the transcript profiles of PpMAPKKK3, PpMAPKK5, and PpMAPK1 were elevated. Subsequently, yeast two-hybrid, luciferase complementation imaging, pull-down, and in vitro phosphorylation assays were conducted to characterize the complete MAPK cascade (PpMAPKKK3-PpMAPKK5-PpMAPK1) involved in peach fruit. Moreover, the downstream events of MAPK1 include the involvement of SNARE13 and the corresponding NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1)-responsive defense. Single silencing of MAPKKK3, MAPKK5, or MAPK1 and double silencing of MAPKKK3 and MAPKK5 or MAPKK5 and MAPK1 resulted in enhanced susceptibility to the fungus R. stolonifer in mutants and attenuated salicylic acid (SA)-dependent defense gene expression. In contrast, the homologous or heterologous overexpression of PpSNARE13 in peach fruit or Arabidopsis led to an enhanced SA pool and elevated expression of pathogenesis related (PR) genes. Reciprocally, the ppsnare13cas9 mutants were generally compromised in the priming of SA-dependent resistance. Therefore, the MAPKKK3-MAPKK5-MAPK1 cascade contributed to pattern-triggered immunity signal transduction in BABA-elicited peach fruit, by combination with downstream events such as SNARE13, NPR1, and SA-dependent signaling.

Non-host resistance (NHR) is the most durable and robust form of innate immunity, with a surge of interest in its role in crop improvement. Of the NHR genes identified against rice blast, a devastating disease caused by Magnaporthe oryzae, Arabidopsis PEN2 is indispensable for pre-penetration resistance to M. oryzae, while a consortium of genes orchestrates post-penetration resistance via lesser known mechanisms. We identified M. oryzae-susceptible mosA (mthfr2 pen2-3) from a randomly mutagenized Arabidopsis pen2-3 population using forward genetics. Analysis of T-DNA-inserted mthfr2 lines and pen2-3-complemented mosA lines revealed that MTHFR2-dependent resistance to M. oryzae is independent of PEN2. MTHFR2-defective plants exhibited higher accumulation of reactive oxygen species and expression of salicylic acid-dependent defense markers. MTHFR2-ligand docking revealed that A55V non-synonymous substitution in mosA altered ligand binding efficiency. This further affected the metabolomic profile of mosA, effectively allowing in vitro germination and development of M. oryzae conidia. Moreover, the loss-of-function mutation in mthfr2 (involved in the 1C metabolic pathway) potentiated mosA immunity against Pst DC3000. In conclusion, our findings showed that MTHFR2 is a positive modulator of NHR against M. oryzae. This work documents another layer of conserved yet divergent metabolomic defense in Arabidopsis regulated by folate-mediated 1C metabolism that has the potential to revolutionize crop improvement.

During leaf senescence, autophagy plays a critical role by removing damaged cellular components and participating in nutrient remobilization to sink organs. However, how AUTOPHAGY (ATG) genes are regulated during natural leaf senescence remains largely unknown. In this study, we attempted to identify upstream transcriptional regulator(s) of ATG genes and their molecular basis during leaf senescence in Arabidopsis through the combined analyses of promoter binding, autophagy flux, and genetic interactions. We found that PHYTOCHROME-INTERACTING FACTOR4 (PIF4) and PIF5 directly bind to the promoters of ATG5, ATG12a, ATG12b, ATG8a, ATG8e, ATG8f, and ATG8g, inducing their transcription. These target ATG genes are down-regulated in pif4, pif5, and pif4pif5 mutants, resulting in decreased autophagic activity and slower degradation of chloroplast proteins and chlorophyll. Conversely, overexpression of ATG8 genes accelerated protein degradation with early leaf senescence. Moreover, our data suggested partial suppression of the pif4pif5 phenotype by ATG8a overexpression. PIF4/PIF5 also influence senescence induced by nutrient starvation, another hallmark of the autophagy pathway. Furthermore, we observed that the PIF4/PIF5-ATG regulatory module may contribute to seed maturation. Our study not only unveils transcriptional regulators of autophagy in natural leaf senescence but also underscores the potential role of PIF4/PIF5 as functional regulators in leaf senescence and nutrient remobilization.

Plant mechanical failure, known as lodging, has detrimental impacts on the quality and quantity of maize yields. Failure can occur at stalks (stalk lodging) or at roots (root lodging). While previous research has focused on proxy measures for stalk stiffness, stalk strength, and root strength, there is a need to quantify the root system stiffness, which quantifies the force-displacement relationship. Here, we report a tool to quantify the root system stiffness of maize hybrids grown in different conditions. The results show that maize hybrids with a higher root system stiffness have a greater susceptibility to root lodging. This result is consistent with expected mechanical behavior, since higher root system stiffness values mean that the plant reaches the failure strength at lower displacements compared with a plant with lower root system stiffness. Collectively, this study describes the first tool to measure root system stiffness and enables a comprehensive understanding of the integrated plant mechanics and lodging.

Potato (Solanum tuberosum) is a staple food worldwide, but modern potato cultivation relies heavily on the use of pesticides to control pests and diseases. However, many wild Solanum species are highly resistant to biotic and abiotic stresses relevant to potato production. Several of those species have been used in potato breeding to confer resistance but this has only been moderately successful. Instead, we propose an alternative approach to utilize the potential of wild Solanum germplasm. Recently, de novo domestication has been suggested to produce more resilient crops: instead of introducing resistance genes into existing crops, domestication traits could be introduced into resistant wild crop relatives to create new crops. Therefore, we selected 10 promising species from the 107 known wild tuber-bearing Solanum species for their resistance to biotic and abiotic stresses. Selection was based on the existing literature, characterizing species by tuberization under short- and long-day conditions, tuber glycoalkaloid content, starch digestibility and performance in tissue culture. Based on this, the highly pest- and disease-resistant S. bulbocastanaum was chosen. Our results showed that it produced relatively large tubers, also under long-day conditions, and performed exceptionally well in tissue culture.

l-Theanine hydrolysis in tea (Camellia sinensis) leaves not only reduces the quality of tea products but also decreases their health benefits. Postharvest dehydration-induced abscisic acid (ABA) contributes to l-theanine hydrolysis, but the specific underlying mechanism has not been explored. Based on transcriptome analysis and gene silencing experiments, CsNCED3a was shown to be a key gene for ABA synthesis in harvested tea leaves, and CsABF7 up-regulated the expression of CsWRKY40, which encodes a transcription factor that directly regulates a l-theanine hydrolysis gene, resulting in the loss of l-theanine. CsWRKY53 and CsWRKY40 activated the expression of CsNCED3a. The CsWRKY53-CsWRKY40 complex exhibited a stronger regulatory effect than the individual transcription factors. These findings reveal an ABA-mediated regulatory pathway for l-theanine hydrolysis, and highlight the pivotal role of ABA in the postharvest metabolism of critical flavor-contributing metabolites in tea leaves.

The phosphatidylethanolamine-binding protein (PEBP) family members FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1) are major regulators of plant reproduction. In Arabidopsis, the FT/TFL1 balance defines the timing of floral transition and the determination of inflorescence meristem identity. However, emerging studies have elucidated a plethora of previously unknown functions for these genes in various physiological processes. Here, we characterized potential roles in seed size and dormancy of FT and TFL1 in Arabidopsis thaliana using CRISPR mutants and reporter analysis. Our findings unveiled a role for TFL1 in seed dormancy while confirming the role of FT in regulating this trait. We showed that the interplay between these two genes in seed dormancy is antagonistic, mirroring their roles in flowering time and inflorescence architecture. Analysis of reporter lines demonstrated that FT and TFL1 are partly co-expressed in seeds. Finally, we showed that total seed yield is affected in these mutants. Together, our results highlight the versatility of these two genes beyond their canonical functions. The impact of FT and TFL1 on seed characteristics emphasizes the significance of approaching gene studies from various perspectives, enabling the identification of multifaceted molecular factors that could play a major role in shaping the future of agriculture.