Deciphering the mechanism of E3 ubiquitin ligases in plant responses to abiotic and biotic stresses and perspectives on PROTACs for crop resistance.

With global climate change, it is essential to find strategies to make crops more resistant to different stresses and guarantee food security worldwide. E3 ubiquitin ligases are critical regulatory elements that are gaining importance due to their role in selecting proteins for degradation in the ubiquitin-proteasome proteolysis pathway. The role of E3 Ub ligases has been demonstrated in numerous cellular processes in plants responding to biotic and abiotic stresses. E3 Ub ligases are considered a class of proteins that are difficult to control by conventional inhibitors, as they lack a standard active site with pocket, and their biological activity is mainly due to protein-protein interactions with transient conformational changes. Proteolysis-targeted chimeras (PROTACs) are a new class of heterobifunctional molecules that have emerged in recent years as relevant alternatives for incurable human diseases like cancer because they can target recalcitrant proteins for destruction. PROTACs interact with the ubiquitin-proteasome system, principally the E3 Ub ligase in the cell, and facilitate proteasome turnover of the proteins of interest. PROTAC strategies harness the essential functions of E3 Ub ligases for proteasomal degradation of proteins involved in dysfunction. This review examines critical advances in E3 Ub ligase research in plant responses to biotic and abiotic stresses. It highlights how PROTACs can be applied to target proteins involved in plant stress response to mitigate pathogenic agents and environmental adversities.

Study on the biocontrol effect and physiological mechanism of Hannaella sinensis on the blue mold decay of apples.

Blue mold decay is a major postharvest disease of apples, causing considerable losses to the apple industry. In the early stage of this research, an antagonistic yeast, Hannaella sinensis, with a good control effect on the blue mold of apples, was selected. On this basis, the main purpose of this work was to study the biocontrol effect of H. sinensis on the blue mold of apples and the mechanisms involved. The results showed that H. sinensis could effectively control the blue mold decay of apples, reduce the rot rate and diameter, and the antagonistic effect strengthened with the increase of H. sinensis concentration (1 × 108 cells/mL). Further in vitro experiments proved that H. sinensis could significantly inhibit the spore germination and germ tube length of P. expansum. In addition, stable colonization of H. sinensis on apple wounds and surfaces confirmed the environmental adaptability and the ability to compete with other microbiota for nutrition and space. Moreover, H. sinensis induced the activities of resistance-related enzymes such as polyphenol oxidase (PPO), peroxidase (POD), ascorbate peroxidase (APX), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) in apples and the content of the coding genes corresponding to these enzymes was also higher than that of the control group. Our results indicate that H. sinensis treatment could induce the disease resistance of apples. In summary, H. sinensis served as a promising antagonistic yeast for the prevention and treatment of postharvest blue mold decay of apples.