N-乙酰葡糖胺抑制淡紫拟青霉产孢的分子机制

The interaction of nematode-parasitic fungi and their hosts is a key issue for biological control of plant-parasitic nematodes. When living as a saprophyte, the nematode-egg-parasitic fungus Paecilomyces lilacinus finishes a life cycle by fast switching between mycelial growth and sporulation. But when infecting nematode eggs, it maintains mycelia branch and extension but inhibits conidiation. This living strategy is favorable for infection, but the mechanism of the regulation is unknown. Our previous study showed that the degrading product of the egg shell chitin, N-acetylglucosamine (GlcNAc), could inhibit conidiation of P. lilacinus. Meanwhile, adding GlcNAc in the media could promote egg infection by the fungus. In this project, our goal is to find key genes involved in the conidiation inhibition. Firstly, we find candidate genes by screening homolog genes of conidiation regulation in model fungi like Aspergillus spp. and, by transcriptome analysis and screening mutation library. Then, these candidate genes were characterized by gene knockout and complementation. Last, we study the role of conidiation inhibition in infection of nematode eggs by comparison the infection rates of mutants of involved genes with wild type strain. All of these study is to achieve in-depth understanding of fungal infection of nematode eggs, and using them to control plant-parasitic nematodes with high efficiency.

线虫病原真菌与宿主线虫的相互作用是研究植物线虫生物防治的关键问题。不同于腐生阶段中菌丝生长与产孢的快速转换的生活方式，线虫卵寄生真菌淡紫拟青霉侵染线虫卵的整个过程中维持大量菌丝的生长并抑制孢子产生。这种生长方式有利于高效侵染的进行，但其中的生长调节机制并不清楚。前期研究发现线虫卵壳几丁质的降解产物N-乙酰葡糖胺（GlcNAc）可以抑制淡紫拟青霉分生孢子的产生，并且外源添加GlcNAc可以提高该菌对线虫卵的侵染能力。本项目拟在前期研究的基础上，借鉴模式真菌产孢调控通路，通过转录组分析，突变体库筛选并结合基因敲除和回补等方法鉴定GlcNAc抑制淡紫拟青霉产孢信号转导途径中的关键基因。通过比较突变菌株产孢和卵寄生能力的变化分析GlcNAc抑制产孢的机制及其在真菌侵染线虫卵过程中的作用，为深入理解真菌侵染线虫卵的分子机制，高效利用该类真菌控制植物寄生线虫奠定基础。

线虫病原真菌与宿主线虫的相互作用是研究植物线虫生物防治的关键问题。不同于腐生阶段中菌丝生长与产孢的快速转换的生活方式，线虫卵寄生真菌淡紫拟青霉侵染线虫卵的整个过程中维持大量菌丝的生长并抑制孢子产生。这种生长方式有利于高效侵染的进行，但其中的生长调节机制并不清楚。前期研究发现线虫卵壳几丁质的降解产物N-乙酰葡糖胺（GlcNAc）可以抑制淡紫拟青霉分生孢子的产生，并且外源添加GlcNAc可以提高该菌对线虫卵的侵染能力。本项目根据研究路线，对淡紫拟青霉进行了全基因组测序，转录组测序分析，在构建了高效的遗传操作系统的基础上重点对淡紫拟青霉的产孢调控基因进行了功能研究，并且对淡紫拟青霉N-乙酰葡糖胺的代谢通路进行了基因功能研究。综上，我们推测N-乙酰葡糖胺抑制淡紫拟青霉产分生孢子的主要机制是Dac1的代谢产物GlcN-6-phosphate可能作为信号分子抑制了分子孢子的产生。而该信号可能通过Ras传导。接下来我们在本项目成果的基础上会进一步的进行相关实验，对该机制进行深入挖掘。本项目为深入理解真菌侵染线虫卵的分子机制，高效利用该类真菌控制植物寄生线虫奠定基础。