Apple SERRATE negatively mediates drought resistance by regulating MdMYB88 and MdMYB124 and microRNA biogenesis

Abstract

The function of serrate (SE) in miRNA biogenesis in Arabidopsis is well elucidated, whereas its role in plant drought resistance is largely unknown. In this study, we report that MdSE acts as a negative regulator of apple (Malus × domestica) drought resistance by regulating the expression levels of MdMYB88 and MdMYB124 and miRNAs, including mdm-miR156, mdm-miR166, mdm-miR172, mdm-miR319, and mdm-miR399. MdSE interacts with MdMYB88 and MdMYB124, two positive regulators of apple drought resistance. MdSE decreases the transcript and protein levels of MdMYB88 and MdMYB124, which directly regulate the expression of MdNCED3, a key enzyme in abscisic acid (ABA) biosynthesis. Furthermore, MdSE is enriched in the same region of the MdNECD3 promoter where MdMYB88/MdMYB124 binds. Consistently, MdSE RNAi transgenic plants are more sensitive to ABA-induced stomatal closure, whereas MdSE OE plants are less sensitive. In addition, under drought stress, MdSE is responsible for the biogenesis of mdm-miR399, a negative regulator of drought resistance, and negatively regulates miRNAs, including mdm-miR156, mdm-miR166, mdm-miR172, and mdm-miR319, which are positive regulators of drought resistance. Taken together, by revealing the negative role of MdSE, our results broaden our understanding of the apple drought response and provide a candidate gene for apple drought improvement through molecular breeding.

Apple Sumo E3 Ligase Mdsiz1 Negatively Regulates Drought Tolerance

“…We speculate that their upregulation may have contributed to the increased drought tolerance of MdSIZ1 RNAi plants. In addition, previous studies have found that the dwarf phenotype may be related to plant miRNA level [6,64] . Our stemloop qRT-PCR analysis demonstrates that the drought positive regulators mdm-miR168 and mdm-miR72 were upregulated in transgenic lines under normal and drought conditions [44,45] .…”

“…RNAi plants under drought stress. The positive regulators of drought stress, MdDREB2A, MdPIP1;3 and MdNCED3 [6,41,43] , were induced to a greater extent in MdSIZ1 RNAi transgenic plants than in GL-3 ( Fig. 9).…”

“…10). These genes are positive regulators of drought response [6,41,43] and MdSIZ1 appears to negatively regulate their expression.…”

“…Water deficiency is the most important challenge in the main Chinese apple producing area on the loess plateau. Hence, it is important to understand the function of key drought-responsive genes and investigate the physiologic mechanisms by which apple trees respond to drought [5,6] . Plants may respond to drought stress by controlling stomatal movement [7] , hormone biosynthesis [8] , the ability to scavenge reactive oxygen species [9] , accumulation of metabolic products [10] , root development [3] , transcriptional regulation [10] and microRNA biogenesis [11] .…”

Fine-tuning of SUMOylation modulates drought tolerance

“…In fruit trees, water deficit inhibits flower bud differentiation and tree vegetative growth, thereby causing flowers and fruits to drop (Virlet et al, 2015; Niu et al, 2019). To cope with drought stress, plants respond at both the morphological and molecular levels, exhibiting changes in photosynthesis, stomatal movement, hormone content, leaf development, stem extension, root proliferation, hydraulic conductivity, and gene expression (Yordanov et al, 2000; Seiler et al, 2011; Basu et al, 2016; Liao et al, 2016; Sun et al, 2018; Geng et al, 2020; Li et al, 2020). Therefore, decoding the molecular mechanisms that underlie drought responses is critical to the development of new cultivars for future agriculture (Sun et al, 2013b; Liao et al, 2016; Geng et al, 2018; Sun et al, 2018; Li et al, 2020).…”