黄曲霉分生孢子色素合成基因pks1的鉴定及其对生长发育和侵染性的影响

Identification of conidial pigment synthetic gene pks1 and its effect on development and pathogenicity in Aspergillus flavus

摘要:

[目的]分生孢子色素是真菌细胞壁的重要成分，对真菌的生长发育极为重要，并有助于真菌抵御各种环境胁迫。本研究鉴定了黄曲霉分生孢子色素合成基因，并研究了分生孢子色素对黄曲霉生长发育及其对抗紫外照射和侵染能力的影响。[方法]通过已知真菌孢子色素合成基因蛋白序列同源比对确定了黄曲霉分生孢子色素合成基因及其所在的基因簇，利用同源重组策略对目标基因进行敲除，获得了该色素合成基因缺失的突变菌株，并研究该基因敲除后对表型、产孢、菌核形成、黄曲霉毒素产生、抗紫外照射和侵染性等影响。[结果]与野生型菌株相比，黄曲霉pks1基因缺失菌株的分生孢子颜色变为白色，生长速度、孢子产量、菌核形成和黄曲霉毒素B₁的产生均没有显著性变化，但该基因的缺失导致孢子对紫外线照射的抵御能力明显减弱，降低了黄曲霉对玉米和花生种子的侵染能力。[结论]pks1（AFLA_006170）基因是黄曲霉分生孢子色素合成的关键基因，影响黄曲霉分生孢子对紫外线照射等不利环境因子的抵抗能力和对粮食种子的侵染能力。

Abstract:

[Objective] The fungal conidial pigments are essential components for the formation of the fungal cell wall. The pigments play very important roles in fungal growth and resistance to various environmental stress responses. Here, the biosynthetic gene of conidial pigment was identified and characterized in Aspergillus flavus. [Methods] By the homologous search of the known pigment biosynthetic gene protein, the key gene involved in the pigment production was identified in A. flavus. The target gene was disrupted using homologous recombination strategy, and the effects of the gene deletion on fungal phenotype, sporulation, sclerotia formation, aflatoxin production, anti-ultraviolet irradiation and invasiveness were investigated. [Results] Compared with the wild-type strain, the Δpks1 mutant lost the conidial color instead of producing the white conidia. No obvious difference was detected in the growth rate, spore yield, formation of stress-resistant structure sclerotia and production of aflatoxin B₁ between WT and Δpks1 mutant strains. However, the deletion of pks1 resulted in a decrease in resistance to UV radiation and the ability to infect corn and peanut seeds. [Conclusion] The pks1 (AFLA_006170) is a key gene for conidia pigment production in A. flavus. The conidial pigment biosynthetic pathway is related to fungal resistance against UV radiation and the infection to cereal crops.