Apple cuticular wax can protect plants from environmental stress, determine fruit luster, and improve post-harvest fruit storage quality. In recent years, dry weather, soil salinization, and adverse environmental conditions have led to declines in apple fruit quality. However, few studies have reported the molecular mechanisms of apple cuticular wax biosynthesis. In this study, we identified a long-chain acyl-CoA synthetase MdLACS2 gene from apple. The MdLACS2 protein contained an AMP-binding domain and demonstrated long-chain acyl-CoA synthetase activity. MdLACS2 transgenic Arabidopsis exhibited reductions in epidermal permeability and water loss; changed in the expression of genes related to cuticular wax biosynthesis, transport, and transcriptional regulation; and differences in the composition and ultrastructure of cuticular wax. Moreover, the accumulation of cuticular wax enhanced the resistance of MdLACS2 transgenic plants to drought and salt stress. The main protein functional interaction networks of LACS2 were predicted, revealing a preliminary molecular regulation pathway for MdLACS2-mediated wax biosynthesis in apple. Our study provides candidate genes for breeding apple varieties and rootstocks with better fruit quality and higher stress resistance.
During vegetative development, higher plants continuously form new leaves in regular spatial and temporal patterns. Mutants with abnormal leaf developmental patterns not only provide a great insight into understanding the regulatory mechanism of plant architecture, but also enrich the ways to its modification by which crop yield could be improved. Here, we reported the characterization of the rice leafy-head2 (lhd2) mutant that exhibits shortened plastochron, dwarfism, reduced tiller number, and failure of phase transition from vegetative to reproductive growth. Anatomical and histological study revealed that the rapid emergence of leaves in lhd2 was resulted from the rapid initiation of leaf primordia whereas the reduced tiller number was a consequence of the suppression of the tiller bud outgrowth. The molecular and genetic analysis showed that LHD2 encodes a putative RNA binding protein with 67% similarity to maize TE1. Comparison of genome-scale expression profiles between wild-type and lhd2 plants suggested that LHD2 may regulate rice shoot development through KNOX and hormone-related genes. The similar phenotypes caused by LHD2 mutation and the conserved expression pattern of LHD2 indicated a conserved mechanism in controlling the temporal leaf initiation in grass.
Post-translational modification of proteins mediated by SIZ1, a small ubiquitin-like modifier (SUMO) E3 ligase, regulates multiple biological processes in plants. However, its role in the regulation of lateral root formation remains unclear. Here, we demonstrate that the apple SUMO E3 ligase MdSIZ1 promotes lateral root formation. Using a yeast-two-hybrid (Y2H) system, the auxin response factor MdARF8 was screened out as a protein-protein interaction partner of the SUMO-conjugating E2 enzyme MdSCE1, indicating that MdARF8 may be a substrate for MdSIZ1. The interaction between MdARF8 and MdSCE1 was confirmed by pull-down, Y2H and Co-immunoprecipitation assays. MdSIZ1 enhanced the conjugating enzyme activity of MdSCE1 to form a MdSCE1-MdSIZ1-MdARF8 complex, thereby facilitating SUMO modification. We identified two arginine substitution mutations at K342 and K380 in MdARF8 that blocked MdSIZ1-mediated SUMOylation, indicating that K342 and K380 are the principal SUMOylation sites of the MdARF8 protein. Moreover, MdARF8 promoted lateral root formation in transgenic apple plants, and the phenotype of reduced lateral roots in the Arabidopsis siz1-2 mutant was restored in siz1-2/MdARF8 complementary plants. Our findings reveal an important role for sumoylation in the regulation of lateral root formation in plants.
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