Transcription factors DkBZR1/2 regulate cell wall degradation genes and ethylene biosynthesis genes during persimmon fruit ripening

Abstract

BZR transcription factors are critical components of the brassinosteroid signaling pathway, but their possible roles in fruit ripening have rarely been reported. In this study, four BZR sequences were isolated from persimmon fruit. Among the four BZR genes, DkBZR1/2 were expressed in persimmon fruit, and a Western blot assay showed that the protein level of DkBZR1 decreased and that dephosphorylated DkBZR2 protein gradually accumulated during the storage period. DkBZR1/2 protein were localized in both the nucleus and cytoplasm and accumulated in the nucleus after 24-epibrassinolide treatment. DkBZR1 can suppress the transcription of DkEGase1 and DkACS1 by binding to the BRRE motif in their promoters and that DkBZR2 can activate the transcription of DkPL1 and DkACO2 by binding to the E-box motif in their promoters. The transient overexpression of DkBZR2 promoted the conversion of acid-soluble pectin to water-soluble pectin and increased ethylene production in persimmon fruit. Our findings indicate that DkBZR1 and DkBZR2 serve as repressors and activators of persimmon fruit ripening, respectively.

Transcriptional regulation of fleshy fruit texture

“…SlBES1‐ OE tomato fruit showed a shorter shelf life with severe wrinkles 13 d after harvest, although no cuticle morphology analysis was performed (Liu et al, 2021a). In persimmon ( Diospyros kaki ), DkBZR1 suppressed the transcription of DkEGase1 , whereas, in contrast, DkBZR2 actually activated the transcription of DkPL1 in a direct manner (He et al, 2021), again illustrating there are activators and repressors for specific genes.…”

“…In addition to ethylene and ABA, plus other hormones, such as indole acetic acid (IAA), brassinosteroid (BR), and jasmonic acid (JA), have been reported to affect fruit ripening and softening. In several cases, these hormones affect ethylene production by modulation of the expression of ACS (1‐amino‐cyclopropane‐1‐carboxylate synthase) and ACO (1‐aminocyclopropane‐1‐carboxylate oxidase) ethylene biosynthetic genes (Li et al, 2021), for example, the BR TFs, MaBZR1/2 and DkBZR1 target on MaACS1, MaACO13/14 and DkACS1 in banana and persimmon (Guo et al, 2019; He et al, 2021), and in plum ( Prunus salicina ), PsABI5 (ABA‐insensitive 5) binds to the PsACS1 promoter (Sadka et al, 2019). At present, the main effects of other phytohormones can be attributed to their role in modulating the expression of ethylene biosynthesis genes, but the situation is complex.…”

Genome-Wide Identification of the Xyloglucan endotransglucosylase/Hydrolase (XTH) and Polygalacturonase (PG) Genes and Characterization of Their Role in Fruit Softening of Sweet Cherry

“…The transient transgenic technology is increasingly applied to the verification of gene functions in fruit research [50,51]. To confirm whether candidate genes are involved in fruit softening, overexpression of these genes in sweet cherry fruit was also performed.…”

Brassinosteroids signaling component SlBZR1 promotes fruit ripening in tomato

“…Additionally, our former research also showed that BR signaling promoted carotenoid accumulation and quality formation in tomato during fruit ripening period [51]. Several recent studies found that MaBZR1/2, PuBZR1 and DkBZR1 repress ethylene production, while DkBZR2 promotes ethylene production during postharvest fruit ripening [42, 52, 53].…”