Red light induces salicylic acid accumulation by activating CaHY5 to enhance pepper resistance against Phytophthora capsici

Pepper(Capsicum annuum L.)is frequently challenged by various pathogens,among which Phytophthora capsici is the most devastating to pepper production.Red light signal acts as a positive induction of plant resistance against multiple pathogens.However,little is known about how the red light signal affects pepper resistance to P.capsici infection(PCI).Here,we report that red light regulates salicylic acid(SA)accumulation by activating elongated hypocotyl5(CaHY5),a basic leucine zipper(bZIP)transcription factor,thereby decreasing pepper susceptibility to PCI.Exogenous SA treatment reduced pepper susceptibility to PCI,while silencing of CaPHYB(a red light photoreceptor)increased its susceptibility.PCI significantly induced CaHY5 expression,and silencing of CaHY5 reduced SA accumulation,accompanied by decreases in the expression levels of phenylalanine ammonia-lyase 3(CaPAL3),CaPAL7,pathogenesis-related 1(CaPR1),and CaPR1L,which finally resulted in higher susceptibility of pepper to PCI.Moreover,CaHY5 was found to activate the expression of CaPAL3 and CaPAL7,which are essential for SA biosynthesis,by directly binding to their promoters.Further analysis revealed that exogenous SA treatment could restore the resistance of CaHY5-silenced pepper plants to PCI.Collectively,this study reveals a critical mechanism through which red light induces SA accumulation by regulating CaHY5-mediated CaPAL3 and CaPAL7 expression,leading to enhanced resistance to PCI.Moreover,red light-induced CaHY5 regulates pepper resistance to PCI,which may have implications for PCI control in protected vegetable production.

The hist one varia nt SI_H2A.Z regulates carote noid biosynthesis and gene expression during tomato fruit ripening

The conserved histone variant H2A.Z is essential for transcriptional regulation;defense responses;and various biological processes in plants,such as growth,development,and flowering.However,little is known about how H2A.Z affects the developmental process and ripening of tomato fruits.Here,we utilized the CRISPR/Cas9 gene-editing system to generate a sl_hta9 sl_hta11 double-mutant,designated sl_h2az,and found that these two mutations led to a signi fi cant reduction in the fresh weight of tomato fruits.Subsequent messenger RNA(mRNA)-seq results showed that dysfunction of SI_H2A.Z has profound effects on the reprogramming of genome-wide gene expression at different developmental stages of tomato fruits,indicating a ripening-dependent correlation between SI_H2A.Z and gene expression regulation in tomato fruits.In addition,the expression of three genes,SIPSY1,SlPDS,and SlVDE,encoding the key enzymes in the biosynthesis pathway of carotenoids,was signi fi cantly upregulated in the later ripening stages,which was consistent with the increased contents of carotenoids in sl_h2a.z double-mutant fruits.Overall,our study reveals a role of SI_H2A.Z in the regulation of carotenoids and provides a resource for the study of SI_H2A.Z-dependent gene expression regulation.Hence,our results provide a link between epigenetic regulation via histone variants and fruit development,suggesting a conceptual framework to understand how histone variants regulate tomato fruit quality.