Search

SUMMARY: Pustule formation is pivotal for the development of the Xanthomonas citri subsp. citri (Xcc)‐induced citrus canker disease (CCD). Although our previous study demonstrated that the exogenous application of abscisic acid (ABA) facilitated pustule formation induced by Xcc, the precise mechanism remains elusive. The 9‐cis‐epoxycarotenoid dioxygenase (NCED) is a crucial enzyme in ABA biosynthesis. This study explored the role of citrus CsNCED1‐1 in CCD resistance through overexpression and RNA interference of CsNCED1‐1 in Wanjincheng orange (Citrus sinensis). Our findings indicated that CsNCED1‐1 negatively modulated CCD resistance by fostering ABA accumulation, concomitant with an increase in jasmonic acid (JA) and a decrease in salicylic acid (SA). Plants overexpressing CsNCED1‐1 displayed shortened leaves with smaller and denser stomata along with irregular and increased palisade cells. CsLOB1 is a known susceptibility gene for CCD, and CsbZIP40 positively influences resistance to this disease. We further confirmed that CsLOB1 promoted and CsbZIP40 suppressed the transcription of CsNCED1‐1 by directly binding to the CsNCED1‐1 promoter. Notably, CsbZIP40 and CsLOB1 showed a competitive relationship in the regulation of CsNCED1‐1 expression, with CsbZIP40 exhibiting greater competitiveness. Overall, our findings highlight that CsNCED1‐1 promotes susceptibility to citrus canker by disrupting JA‐ and SA‐mediated defense mechanisms and triggering the proliferation and remodeling of palisade cells, thereby facilitating pathogen colonization and pustule formation. This study offers novel insights into the regulatory mechanisms underlying citrus canker resistance and the role of CsNCED1‐1 in citrus. [ABSTRACT FROM AUTHOR]

Jasmonic acid (JA), a plant endogenously synthesized lipid hormone, plays an important role in response to stress. This manuscript summarized the biosynthesis and metabolism of JA and its related regulatory mechanisms, as well as the signal transduction of JA. The mechanism and regulatory network of JA in plant response to biotic and abiotic stresses were systematically reviewed, with the latest advances highlighted. In addition, this review summarized the signal crosstalk between JA and other hormones in regulating plant resistance to various stresses. Finally, the problems to be solved in the study of plant stress resistance mediated by JA were discussed, and the application of new molecular biological technologies in regulating JA signaling to enhance crop resistance was prospected, with the aim to facilitate future research and application of plant stress resistance.