MdMADS6 Recruits Histone Deacetylase MdHDA19 to Repress the Expression of the Carotenoid Synthesis-Related Gene MdCCD1 during Fruit Ripening

Abstract

Fruit ripening is regulated by epigenetic modifications and transcription factors, which may function independently or as protein complexes. Our previous study showed that the apple histone deacetylase19 (MdHDA19) suppresses fruit ripening through the deacetylation of histones in related genes. Here, a MADS-box transcription factor (MdMADS6) was identified using a yeast two-hybrid (Y2H) assay as a candidate protein that interacts with MdHDA19 during apple fruit ripening. Furthermore, Y2H, bimolecular fluorescence complementation (BiFC) and pull-down assays were used to confirm the interaction between MdHDA19 and MdMADS6. Agrobacterium-mediated transient transformation and yeast one-hybrid assays showed that MdMADS6 promoted carotenoid accumulation in apple fruit by acting on the downstream target genes related to carotenoid biosynthesis. In summary, we conclude that, in the early stages of fruit development, the expression of MdMADS6 was maintained at lower levels, where it interacted with MdHDA19 to form a protein complex that inhibited the expression of the downstream genes. At the late stages of fruit development, active expression of MdMADS6 dissociated the protein complex of MdMADS6 and MdHDA19 and consequently promoted the expression of carotenoid biosynthesis genes as well as carotenoid accumulation.

Molecular regulation of apple and grape ripening: exploring common and distinct transcriptional aspects of representative climacteric and non-climacteric fruits

“…MdHDA19, promoting H3k9 deacetylation, can form a MdERF4–dTPL4 complex repressing the expression of MdACS3a gene, specifically active in the early maturation phase. MdHDA19 was furthermore found to interact with MdMADS6, which in turn promoted carotenoid accumulation in apple fruit ( Q. Li et al ., 2022 ).…”

Involvement of Transcription Factors and Regulatory Proteins in the Regulation of Carotenoid Accumulation in Plants and Algae

“…Recently, multiple MADS transcription factors, such as SlRIN, SlCMB1, and SlTAGL1 in tomato, − CsMADS3/5/6 in citrus, ,, and AcMADS32 in kiwifruit, could positively regulate carotenoid metabolism; in contrast, some MADS transcription factors, such as tomato SlMADS1, SlFYFL, and SlMBP8 − as well as apple MdMADS6, could negatively regulate carotenoid accumulation during fruit ripening. In citrus fruits, CsMADS6 activated the transcription of PSY , PDS , and CCD1 genes by directly binding to their promoters .…”

“…MADS, which is named after the first letters of the four transcription factors first identified in this family, mini chromosome maintenance 1 (MCM1) from Saccharomyces cerevisiae, agamous (AG) from Arabidopsis, deficiens (DEF) from Antirrhinum majus, as well as human serum response factor (SRF), 46 is a transcription factor family extensively involved in the regulation of carotenoid metabolism (Table 2 recognizing and binding the CArG-box (CC-A-rich-GG, also known as MADS-box) of the target gene promoter. 47 Recently, multiple MADS transcription factors, such as SlRIN, SlCMB1, and SlTAGL1 in tomato, 48−50 CsMADS3/5/ 6 in citrus, 13,51,52 and AcMADS32 in kiwifruit, 53 could positively regulate carotenoid metabolism; in contrast, some MADS transcription factors, such as tomato SlMADS1, SlFYFL, and SlMBP8 54−56 as well as apple MdMADS6, 57 could negatively regulate carotenoid accumulation during fruit ripening. In citrus fruits, CsMADS6 activated the transcription of PSY, PDS, and CCD1 genes by directly binding to their promoters.…”

Genome-wide characterization and expression analysis of MADS-box transcription factor gene family in Perilla frutescens

“…Apart from their involvement in flower organ development and other processes, these genes also play a vital role in regulating substance metabolism in plants. For instance, CsMADS6 ( AGAMOUS -like subfamily) in citrus, MdMADS6 from apple, and CaMADS-RIN ( SEP subfamily) in pepper have been found to have significant regulatory roles in the carotenoid synthesis pathway ( Dong et al., 2014 ; Lu et al., 2018 ; Li et al., 2022 ). It has been reported that PfMADS genes may be involved in the flavonoid synthesis pathway of P. frutescens ( Jiang et al., 2020 ).…”