Apple SUMO E3 ligase MdSIZ1 regulates cuticular wax biosynthesis by SUMOylating transcription factor MdMYB30

Quantitative Trait Loci Analysis and Marker Development for Fruit Rot Resistance in Cranberry Shows Potential Genetic Association with Epicuticular Wax

Fruit rot is a fungal disease complex that threatens cranberry yields in North American growing operations. Management of fruit rot is especially difficult because of the diversity of the infecting fungal species, and although infections take place early in the season, the pathogens usually remain latent in the ovary until the fruit ripen. Control methods heavily rely on fungicide applications, a practice that may be limited in viability long term. Breeding for fruit rot resistance (FRR) is essential for sustainable production. It is likely that field resistance is multifaceted and involves a myriad of traits that fortify cranberry plants against the biotic and abiotic stresses contributing to fruit rot. In this study, we identified quantitative trait loci (QTL) for FRR in a segregating population. Interestingly, a QTL associated with resistance was found to overlap with one associated with fruit epicuticular wax (ECW). A single-nucleotide polymorphism genotyping assay successfully identified accessions that exhibit the desired phenotypes (i.e., less rot and more ECW), thus making it a useful tool for marker-assisted selection. Candidate genes that may contribute to FRR and ECW were also identified. This work will expedite breeding for improved cranberry fruit quality.

Small ubiquitin-like modifiers E3 ligases in plant stress

Plants regularly encounter various environmental stresses such as salt, drought, cold, heat, heavy metals and pathogens, leading to changes in their proteome. Of these, a post-translational modification, SUMOylation is particularly significant for its extensive involvement in regulating various plant molecular processes to counteract these external stressors. Small ubiquitin-like modifiers (SUMO) protein modification significantly contributes to various plant functions, encompassing growth, development and response to environmental stresses. The SUMO system has a limited number of ligases even in fully sequenced plant genomes but SUMO E3 ligases are pivotal in recognising substrates during the process of SUMOylation. E3 ligases play pivotal roles in numerous biological and developmental processes in plants, including DNA repair, photomorphogenesis, phytohormone signalling and responses to abiotic and biotic stress. A considerable number of targets for E3 ligases are proteins implicated in reactions to abiotic and biotic stressors. This review sheds light on how plants respond to environmental stresses by focusing on recent findings on the role of SUMO E3 ligases, contributing to a better understanding of how plants react at a molecular level to such stressors.

MdDEWAX decreases plant drought resistance by regulating wax biosynthesis

Apple epidermal wax protects plants from environmental stresses, determines fruit gloss and improves postharvest storage quality. However, the molecular mechanisms underlying the biosynthesis and regulation of apple epidermal waxes are not fully understood. In this study, we isolated a MdDEWAX gene from apple, which localized in the nucleus, expressed mainly in apple fruit, and induced by drought. We transformed the MdDEWAX gene into Arabidopsis, and found that heterologous expression of MdDEWAX reduced the accumulation of cuticular waxes in leaves and stems, increased epidermal permeability, the rate of water loss, and the rate of chlorophyll extraction of leaves and stems, altered the sensitivity to ABA, and reduced drought tolerance. Meanwhile, overexpression or silencing of the gene in the epidermis of apple fruits decreased or increased wax content, respectively. This study provides candidate genes for breeding apple cultivars and rootstocks with better drought tolerance.

Insights into the molecular mechanisms underlying responses of apple trees to abiotic stresses

Apple (Malus[Formula: see text]domestica) is a popular temperate fruit crop worldwide. However, its growth, productivity, and quality are often adversely affected by abiotic stresses such as drought, extreme temperature, and high salinity. Due to the long juvenile phase and highly heterozygous genome, the conventional breeding approaches for stress-tolerant cultivars are time-consuming and resource-intensive. These issues may be resolved by feasible molecular breeding techniques for apples, such as gene editing and marker-assisted selection. Therefore, it is necessary to acquire a more comprehensive comprehension of the molecular mechanisms underpinning apples' response to abiotic stress. In this review, we summarize the latest research progress in the molecular response of apples to abiotic stressors, including the gene expression regulation, protein modifications, and epigenetic modifications. We also provide updates on new approaches for improving apple abiotic stress tolerance, while discussing current challenges and future perspectives for apple molecular breeding.