E3 Ubiquitin Ligases Involved In MaMYB4 Regulation Of Cell Wall-metabolism Genes In Banana Fruit Ripening

Banana,as a climacteric fruit,is easy to ripening and softening after harvest,which causes great difficulty in storage and transporation.Therefore,it is of great significance to study ripening mechanism of banana fruit during postharvest storage.Fruit softening is an important factor to quality formation of banana,and fruit softening is closely related to the expression of genes involved in cell wall metabolism.It has been reported that MYB transcription factors play an important role in the growth and development of plants,and E3 ubiquitin ligases participate in various physiological reactions in plants by mediating the ubiquitination of proteins.Previous research indicated that Ma MYBs can regulate starch degradation of banana fruit through suppressing the expression of Ma GWD1,Ma AMY3,etc.However,little information is available whether MYB transcription factors affect banana fruit softening by regulating cell wall-metabolism genes,and E3 ubiquitin ligases with relation to MYBs regulating fruit softening.In this study,based on the report that Ma MYB4 is involved in the banana ripening,Ma MYB4 regulating fruit ripening with relation to E3 ubiquitin ligase Ma BRG3 and cell wall-metabolism genes was studied using real-time quantitative PCR(RT-q PCR),yeast double-hybrid(Y2H)and electrophoresis mobility shift assay(EMSA).The main results are as follows:1.Ma MYB4 is involved in the regulation of banana fruit ripening: RT-q PCR results showed that expression of cell wall metabolism genes(Ma EXP1/2,Ma PG1/3,Ma XTH5/10 and Ma CEL)were up-regulated during banana ripening,and EMSA and Ch IP-q PCR indicated that Ma MYB4 can regulate banana fruit ripening by binding promoters of cell wall metabolism genes(Ma EXP1/2,Ma PG1/3,Ma XTH5/10 and Ma CEL).2.Overexpression of Ma MYB4 in tomato delays fruit ripening: Compared with wild-type fruit,overexpression of Ma MYB4 in tomato delays fruit ripening,and accumualtions of cell wall metabolism genes were inhibited,indicating that Ma MYB4 may regulate fruit ripening by repressing the expression of cell wall metabolism genes.3,E3 ubiquitin ligase Ma BRG3 is involved in Ma MYB4 regulation of banana fruit ripening: Through analysising CDS sequence and amino acid sequence of Ma BRG3 indicated that Ma BRG3 belongs to RING-finger type E3 ubiquitin ligase;Subcellular localization showed that Ma BRG3 localization in the nucleus and was nucleus protein;Ma BRG3 can attenuate the transcriptional repression ability of Ma MYB4 to Ma EXP1/2,Ma PG1/3,Ma XTH5/10 and Ma CEL,involved in the regulation of banana fruit ripening.