MaMYB4 is a negative regulator and a substrate of RING‐type E3 ligases MaBRG2/3 in controlling banana fruit ripening

Abstract

Fruit ripening is a complex developmental process, which is modulated by both transcriptional and posttranslational events. Control of fruit ripening is important in maintaining moderate quality traits and minimizing postharvest deterioration. In this study, we discovered that the transcription factor MaMYB4 acts as a negative regulator of fruit ripening in banana. The protein levels of MaMYB4 decreased gradually with banana fruit ripening, paralleling ethylene production, and decline in firmness. DNA affinity purification sequencing combined with RNA-sequencing analyses showed that MaMYB4 preferentially binds to the promoters of various ripening-associated genes including ethylene biosynthetic and cell wall modifying genes. Furthermore, ectopic expression of MaMYB4 in tomato delayed tomato fruit ripening, which was accompanied by downregulation of ethylene biosynthetic and cell wall modifying genes. Importantly, two RING finger E3 ligases MaBRG2/3, whose protein accumulation increased progressively with fruit ripening, were found to interact with and ubiquitinate MaMYB4, contributing to decreased accumulation of MaMYB4 during fruit ripening. Transient overexpression of MaMYB4 and MaBRG2/3 in banana fruit ripening delayed or promoted fruit ripening by inhibiting or stimulating ethylene biosynthesis, respectively. Taken together, we demonstrate that MaMYB4 negatively modulates banana fruit ripening, and that MaMYB4 abundance could be regulated by protein ubiquitination, thus providing insights into the role of MaMYB4 in controlling fruit ripening at both transcriptional and post-translational levels.

Banana MabHLH28 positively regulates the expression of softening-related genes to mediate fruit ripening independently or via cooperating with MaWRKY49/111

“…In addition, as previous work has revealed that MaWRKY49/111 physically interact with MabZIP21 [ 25 ], further investigations were needed to study the biochemical and genetic machinery of how MabHLH28, MaWRKY49/111, and MabZIP21 proteins act together to mediate banana fruit ripening and softening. Moreover, given the previous findings that MaMYB4 interacts with MaBRG2/3 and MaMAPK14 to undergo protein modifications [ 62 , 63 ], functional connectivity between MabHLH28 and the proteins involved in protein modifications presents opportunities for stripping away MabHLH28 under post-translational regulation during fruit ripening in a future direction.…”

“…DAP-Seq was conducted by the procedure previously described by Yang et al. [ 62 ]. The gDNA was extracted from banana fruit to construct the sequencing library.…”

“…The MaWRKY49 , MaWRKY111 , and MabHLH28 coding sequences were constructed into the pSPYNE and pSPYCE vectors, respectively. The constructs were co-transformed into tobacco and YFP signal was observed (excitation at 514 nm and emission at 525–546 nm) as described previously [ 62 ].…”

E3 ubiquitin ligase MaRZF1 modulates high temperature‐induced green ripening of banana by degrading MaSGR1

“…Cell‐free and in vivo protein degradation tests were conducted as described previously (Yang et al, 2022). MaRZF1‐His fusion proteins exhibited transient expression in the N. benthamiana leaf tissue for cell‐free degradation assay, and the total proteins were subsequently extracted.…”

Emerging Roles of Mitogen-Activated Protein Kinase Signaling Pathways in the Regulation of Fruit Ripening and Postharvest Quality

“…These results demonstrated that the MdMAPK3-MdNAC72 signaling module plays an important role in apple fruit ripening [ 59 ]. A study by Yang et al (2022) [ 31 ] showed that the protein level of the TF MaMYB4 decreased along with banana fruit ripening, which was coupled with ET production and a decline in firmness. MaMYB4 could bind to the promoters of a series of ripening-associated genes, including ET biosynthetic and cell-wall-modifying genes.…”