磷、铁胁迫对棘孢木霉根际定殖的影响

Effects of Phosphorus and Iron Stress on Rhizosphere Colonization of Trichoderma asperellum

磷和铁均为植物生长发育所必需的营养元素,但在土壤中大多以植物难以吸收利用的难溶或微溶性化合物形式存在。木霉菌(Trichoderma sp.)是植物根际有益真菌,在缺铁条件能够产生将不溶性铁转化为可溶性铁的嗜铁素,在促进植物生长、缓解生物及非生物胁迫等方面起着重要作用。但磷胁迫对嗜铁素的合成以及磷,铁胁迫对木霉菌在植物根际定殖的影响尚未见研究。本试验发现,磷胁迫同样能提高嗜铁素产量以及嗜铁素合成相关基因sidA的表达,采用抗利福平标记法测定棘孢木霉菌(Trichoderma asperellum)T6以及sidA敲除突变株△sidA在拟南芥根际的定殖能力,发现在缺磷、缺铁培养基中,棘孢木霉菌(T.asperellum)T6在拟南芥根际的定殖量分别是含磷、含铁对照组的3倍和2.l倍,与△sidA相比分别提高1.7倍和0.9倍,而△sidA在两种培养基中的定殖量却无显著性差异,由此可见,磷、铁胁迫下棘孢木霉菌(T.as-perellum)产生的嗜铁素能够提高菌体在植物根际的定殖。

Phosphorus and iron are essential nutrients for plant growth and development,but most ofthem exist in the form of insoluble or slightly soluble compounds,which are difficult for plants to ab-sorb and utilize in soil.Trichoderma sp.is a beneficial rhizosphere fungus that can produce sid-erophore,and can transform insoluble iron into soluble iron under the iron deficiency condition andplay an important role in promoting plant growth,alleviating biological and abiotic stress.However,the effect of phosphorus stress on the synthesis of siderophore and the effects of phosphorus and ironstress on the colonization of Trichoderma sp.in plant rhizosphere have not been studied by the otherresearchers.In this study,we found that phosphorus stress can also increase the production of sid-erophore and the expression of sidA,a gene related to siderophore synthesis.A rifampin-resistant la-beling method was used to determine the colonization ability of Trichoderma asperellum T6 and sidAgene knockout mutant△sidA in Arabidopsis rhizosphere.The colonization of Trichoderma asperel-lum T6 in the phosphorus-deficient and iron-deficient medium was 3 times and 2.1 times as much ascontrol groups containing phosphorus and iron,respectively,and was 1.7 times and 0.9 times higherthan that of△sidA.However,the colonization of△sidA in above two kinds of medium was not sig-nificantly different.It can be concluded that the siderophore produced by Trichoderma asperellumunder phosphorus and iron stress can improve the colonization of rhizosphere.