Abstract
BackgroundFruit ripening is an intricate developmental process driven by a highly coordinated action of complex hormonal networks. Ethylene is considered as the main phytohormone that regulates the ripening of climacteric fruits. Concomitantly, several ethylene-responsive transcription factors (TFs) are pivotal components of the regulatory network underlying fruit ripening. Calmodulin-binding transcription activator (CAMTA) is one such ethylene-induced TF implicated in various stress and plant developmental processes.ResultsOur comprehensive analysis of the CAMTA gene family in Durio zibethinus (durian, Dz) identified 10 CAMTAs with conserved domains. Phylogenetic analysis of DzCAMTAs, positioned DzCAMTA3 with its tomato ortholog that has already been validated for its role in the fruit ripening process through ethylene-mediated signaling. Furthermore, the transcriptome-wide analysis revealed DzCAMTA3 and DzCAMTA8 as the highest expressing durian CAMTA genes. These two DzCAMTAs possessed a distinct ripening-associated expression pattern during post-harvest ripening in Monthong, a durian cultivar native to Thailand. The expression profiling of DzCAMTA3 and DzCAMTA8 under natural ripening conditions and ethylene-induced/delayed ripening conditions substantiated their roles as ethylene-induced transcriptional activators of ripening. Similarly, auxin-suppressed expression of DzCAMTA3 and DzCAMTA8 confirmed their responsiveness to exogenous auxin treatment in a time-dependent manner. Accordingly, we propose that DzCAMTA3 and DzCAMTA8 synergistically crosstalk with ethylene during durian fruit ripening. In contrast, DzCAMTA3 and DzCAMTA8 antagonistically with auxin could affect the post-harvest ripening process in durian. Furthermore, DzCAMTA3 and DzCAMTA8 interacting genes contain significant CAMTA recognition motifs and regulated several pivotal fruit-ripening-associated pathways.ConclusionTaken together, the present study contributes to an in-depth understanding of the structure and probable function of CAMTA genes in the post-harvest ripening of durian.
Highlights
Fruit ripening is an intricate developmental process driven by a highly coordinated action of complex hormonal networks
Taken together, the present study contributes to an in-depth understanding of the structure and probable function of Calmodulin-binding transcription activator (CAMTA) genes in the post-harvest ripening of durian
Our results positioned DzCAMTA3 and DzCAMTA8 as the key members of the regulatory framework underlying the post-harvest ripening of durian
Summary
Fruit ripening is an intricate developmental process driven by a highly coordinated action of complex hormonal networks. Calmodulin-binding transcription activator (CAMTA) is one such ethylene-induced TF implicated in various stress and plant developmental processes. Several ethylene biosynthesis and signaling genes had been reported to play crucial roles in fruit ripening [2,3,4]. CAMTAs were first reported as an early ethyleneresponsive (NtER) gene implicated in ethylene-regulated plant death and senescence, indicating its probable role in prolonging the shelf life of crops [18]. Apart from the notable involvement of CAMTAs in stress and hormonal biology, a unique involvement of Solanum lycopersicum CAMTAs (SlSRs) in fruit development and ripening has been reported [27]. The treatment of mature green wildtype fruit with ethylene transiently enhanced the expression of all SlSRs [27]
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