EjCaM7 and EjCAMTA3 synergistically alleviate chilling-induced lignification in loquat fruit by repressing the expression of lignin biosynthesis genes under cold stress

Flesh lignification is a typical chilling injury (CI) symptom of loquat fruit during cold storage. [Calcium](D:/D%E7%9B%98/Youdao/Dict/8.9.9.0/resultui/html/index.html) [chloride](D:/D%E7%9B%98/Youdao/Dict/8.9.9.0/resultui/html/index.html) (CaCl 2 ) could enhance chilling tolerance in loquat fruit, but the molecular mechanism is still not illuminated. In this study, CaCl 2 treatment suppressed the increase in firmness and lignin content, and retained higher extractable juice, thereby alleviating chilling-induced lignification in loquat fruit. Moreover, CaCl 2 enhanced the [calmodulin](javascript:;) (CaM) content, free Ca 2+ distribution, EjCaM7 , and CaM binding transcription activators 3 ( EjCAMTA3 ) expression in loquat fruit during cold storage, indicating Ca 2+ /CaM-CAMTA played a key role in response to cold stress. The EjCAMTA3 and EjCaM7 proteins were identified and characterized from loquat fruit. Importantly, EjCAMTA3 bound to the CG-box in EjPODP7-like and EjLAC12-like promoters to repress their transcription. Further analysis revealed that EjCaM7 interacted with EjCAMTA3 in a Ca 2+ -dependent manner, and this interaction enhanced the EjCAMTA3-mediated transcriptional repression of EjPODP7-like and EjLAC12-like genes. Taken together, these findings suggested that CaCl 2 treatment alleviates chilling-induced lignification in loquat fruit, which probably via the synergistic role of EjCaM7 and EjCAMTA3 in the modulation of EjPODP7-like and EjLAC12-like genes expression, leading to the repression of lignin polymerization.