Ethylene‐activated PpERF105 induces the expression of the repressor‐type R2R3‐MYB gene PpMYB140 to inhibit anthocyanin biosynthesis in red pear fruit

Abstract

SummaryEthylene induces anthocyanin biosynthesis in most fruits, including apple (Malus domestica), strawberry (Fragaria × ananassa), and plum (Prunus spp.). However, ethylene inhibits anthocyanin biosynthesis in pear (Pyrus spp.), but the underlying molecular mechanism has not been characterized. In this study, ethylene induced the expression of PpERF105, which encodes a transcription factor. PpERF105 functioned as a transcriptional activator, but it inhibited anthocyanin biosynthesis in pear. A transcriptome analysis revealed that PpERF105 activated the expression of PpMYB140, which encodes an R2R3‐MYB transcriptional repressor. Moreover, PpMYB140 directly inhibited the expression of anthocyanin‐related structural genes. It also competed with PpMYB114 for the binding to bHLH3, ultimately resulting in the formation of the MYB140‐bHLH‐WDR complex rather than the conventional MBW complex, thereby further inhibiting anthocyanin biosynthesis. Furthermore, PpMYB140 prevented the overaccumulation of anthocyanins in the absence of ethylene. Collectively, our study data indicate that ethylene‐induced PpERF105 inhibits anthocyanin biosynthesis by upregulating PpMYB140 expression. Our findings may be useful for elucidating the molecular basis of the ethylene‐mediated inhibition of anthocyanin biosynthesis in fruit.

Pear Fruits Ripening Response to Ethylene and Temperature Treatments

“…Results in tables 2,3 and 4 showed that the compote cultivar records the lowest values (P≤0.05) of weight loss (1.59 and 3.78%), total acidity (0.87 and 1.41%), peroxidase enzyme activity (2.53 and 1.84 absorbing unit/minute/ml) for both study seasons, chlorophyll b (0.09 mg/ml) and total chlorophylls (0.17 mg/ml) for second season, whereas it records the highest values of fruit firmness (14,13 and 20.42 Kg/cm 2 ), total sugars (16.72 and 12.26%), TSS (12.90 and 13.00%) for both seasons, a, b and total chlorophylls and total carotenoids (0.08, 0.14, 0.22 and 0.09 mg/ml) for first season compared to spadona cultivar. Although, the time of fruit maturing and remaining on trees was different between spadona and compote cultivars; June for spadona and October for compote (Table 1), most of the differences in characteristics of the two studied cultivars are controlled by genetic factors [18] as a result of differences in internal hormones, enzyme activities, and fruit structure, where fruits with more cells density and less internal spaces are firmer [19,20], which reflects on the characteristics of the cultivars of the same species to a significant level, as shown in weight loss, fruit firmness and total sugars (Table 3 and 4). Regarding ripening treatments, from the results of the same tables, it appears that the control had the slower ripening process for both seasons where it recorded the lowest values of weight loss (0%), total sugars (12.11 and 8.55%), TSS (11.90 and 11.77%), peroxidase enzyme activity (2.50 and 2.38%) and total carotenoids (0.04 and 0.14 mg/ml) compared to other ripening treatments that record highest values significantly of fruits firmness (14.97 and 19.00 Kg/cm 2 ), total acidity (1.59 and 1.83 %) and total chlorophylls (0.27 and 0.38 mg/ml) for both seasons respectively.…”

Cloning, Subcellular Location and Expression Analysis of Grape MYB Gene

“…Zhu et al 15 found VvMYBC2L2 gene weakly expressed during the fruit development in grapevine, it suggested that VvMYBC2L2 gene played a role as a negative function of anthocyanin biosynthesis. Ni et al 22 studied that Ethylene-activated PpERF105 induced the expression of PpMYB140 to inhibit anthocyanin biosynthesis, and then the PpMYB140 gene played a negative function in red pear fruit. The results of these studies are consistent with the results of this study, suggesting that VvMYBB1 gene and VvMYBA3 gene have a negative effect on the formation of grape skin color of 'Yatomi Rose' grape.…”

Significance of miRNA in enhancement of flavonoid biosynthesis

“…Other studies have shown that in addition to structural genes directly acting on the flavonoid pathway, most miRNA can indirectly participate in the regulation of flavonoid biosynthesis by target transcription factors (Table 2). With further research on transcription factors in plants, it has been found that they individually or jointly regulate flavonoid metabolism and respond to various biotic and abiotic stresses (Xu et al 2015;Ni et al 2021). In A. thaliana, most genes in the metabolic pathway of phenylpropane are regulated by MBW.…”

“…The role of MYB111 in response to salt stress is speculated to be achieved primarily through its regulation of flavonoid biosynthesis (Li et al 2019). Ethylene-activated Pp ethylene response factor 105 (PpERF105) induces expression of the repressor-type R2R3-MYB gene PpMYB140 to inhibit anthocyanin biosynthesis in red pear fruit (Ni et al 2021). Although some miRNAs have been reported to be associated with abiotic stress responses in plants, systematic studies on stress-related miRNAs and their targets in plants remain limited.…”