采后病原真菌耐受UV-C的分子机制

Fungal pathogen attack is one the most devastating threats causing huge losses of postharvest fruits and vegetables. Ultraviolet-C light (UV-C, 190-280 nm wavelength), due to its ability to induce defense reaction in plants and to cause fungicidal effect over microbial pathogens, offers interesting possibilities for controlling postharvest diseases as safe alternative to conventional chemical fungicides. However, fungi usually possess UV-C resistance potential, while in postharvest fungal pathogens the mechanisms to cope with UV-C stress are poorly elucidated. Our preliminary investigation on the model necrotrophic plant pathogen Botrytis cinerea has proved that a gene predicted to encode for endonuclease, Bcuve1, is required for UV-C resistance, and light can induce the expression of Bcuve1 and increase UV-C resistance via the conserved photo receptor White collar 1 (or BcWC1 in B. cinerea). So from the perspective of postharvest pathology, this project plans to employ molecular genetics, biochemistry, and cytology tools to reveal the function of BcUVE1 in anti UV-C stress, and the regulation mechanisms of light signal for the expression of Bcuve1. Furthermore, the regulatable expression patterns of UV-C sensitivity found in B. cinerea will be referred by studies on control efficiencies of UV-C over several other common fungal postharvest pathogens. In general, this project aims to lay a theoretical foundation to improve the beneficial effect of UV-C for postharvest disease management.

病原真菌是导致果蔬采后损失的主要原因之一。短波紫外（UV-C）能破坏微生物DNA结构而起到抑菌作用，也能诱导植物的抗病性，具有开发新型安全采后保鲜措施的潜能。然而，真菌也能产生对UV-C的耐受性，但采后病原真菌对UV-C耐受的分子机制及其调控机理尚不清楚。项目组在前期研究中发现采后重要致病真菌灰霉菌的核酸内切酶基因Bcuve1与耐受UV-C胁迫有关，且光照和光受体BcWC1能调控灰霉菌Bcuve1的表达和对UV-C的敏感性。本研究拟从果实采后病理学的角度，通过遗传、生化、细胞水平的研究方法，解析灰霉菌BcUVE1在UV-C胁迫中的生物学功能，以及光信号经光受体BcWC1调控Bcuve1表达的机理，进而参考灰霉菌对UV-C敏感性受光信号调控的模式，探究光照条件对UV-C抑制其它采后病原真菌的影响，旨在为优化UV-C对果实采后病害的防治效果奠定理论基础。

病原真菌感染是导致果蔬采后损失的重要原因之一，短波紫外（UV-C）是一种清洁环保、极具开发潜力的病害防治措施，它能破坏微生物DNA起到杀菌作用。然而病原菌对UV-C损伤存在一定的修复性，但其UV-C耐受的分子机制及其调控机理尚不清楚。本研究以-病原真菌灰霉菌（Botrytis cinerea）为对象，研究发现光信号对其耐受UV-C有显著的调节作用：与黑暗相比，灰霉菌在蓝、白光下经UV-C照射后菌落存活率显著增强，而红光却无影响。转录表达分析发现，灰霉菌光修复途径基因Bcphr1和DNA选择切除修复途径基因Bcuve1的表达受白光和蓝光的显著诱导；对Bcphr1和Bcuve1进行单突变、双突变基因敲除，发现这两个基因不参与对灰霉菌生长发育和致病性的调控，但二者协同修复DNA损伤，其中Bcuve1起主导作用，而Bcphr1主要发挥光修复功能。亚细胞定位分析表明BcUVE1定位于细胞核，预示着与细胞核内DNA损伤的修复有关。果实接种灰霉菌实验表明，UV-C（1kJ/m2）处理过的带病样品，在红光和黑暗条件下病情被有效控制，而白光和蓝光条件下果实仍然发病严重，表明光照可调节灰霉菌对紫外短波的耐受力。指状青霉(Penicillium digitatum)、胶孢炭疽菌(Colletotrichum gloeosporioides)、链格孢菌(Alternaria alternate)三种采后病原真菌耐受UV-C的能力受光信号调节的特性与灰霉菌一致。综上，采后病原真菌耐受UV-C受光信号调节这一普遍规律的揭示，将为挖掘UV-C在果蔬采后保鲜方面的应用潜力提供新的思路。