Effect Of Piriformospora Indica On Rice Rhizosheath Formation Under Water Stress

Piriformospora indica(P.indica)is an endophytic fungus in the roots of plants that is physiologically and functionally very similar to Arbuscularmycorrhizal fungi(AMF).P.indica has a wide range of parasitic species,which promotes its growth and development and resists abiotic stress.Water stress is the most important abiotic stress in rice growth process,while rhizosheath has the function of water retention and drought resistance.The formation of rhizosheath helps rice to respond to water stress.Rhizosheath are the result of soil,root,and microbial interactions and are closely related to root growth.In this paper,rice were used as research materials,and use microbiome and RNA-seq to explore the working methods of P.indica to promote the formation of rice rhizosheath.The main results are as follows:1.Establish a co-colonization system to study the growth promotion in rice.By studying the colonization effects of different media,it was found that rice and P.indica had the best colonization effect in plant nutrient medium(PNM).Compared to the control,rice colonized by P.indica has a longer main root and higher biomass.Optical microscope can can observe the chlamydospores of P.indica in rice roots.In addition,The Pitef1 gene of P.indica was expressed in rice roots,indicating that P.indica has successfully colonized rice.2.Under water stress,P.indica promoted the formation of rhizosheath and root growth in rice,a process related to proton secretion.By observing the growth phenotype of rice grown and uncolonized P.indica under different water treatments,we found that rice rhizosheath of P.indica was colonized were significantly increased compared to uncolonized rice under moderate drought.The root length of Nipponbare and Zhonghua 35,which colonized by P.indica has also increased significantly.In pH display on medium,we found that P.indica promoted the secretion of protons in the roots of Nipponbare and Zhonghua 35,and also increased the activity of H~+-ATPase in the plasma membrane of these two rice varieties.The activity of root plasma membrane H~+-ATPase was found to be positively correlated with the amount of rhizosheath formed.3.Under water stress,P.indica affected the microbial structure inside and outside the root,increased the abundance of Bacillus in the rhizosheath and root of rice,and reduced the abundance of Fusarium in rhizosheath and root of rice,which may help root growth and rhizosheath formation.The colonization of P.indica significantly reduced the bacterial community richness and increased the diversity of fungal community in rice rhizosheath,and significantly increased the microbial community richness and bacterial community diversity in roots under moderate drought.Through the analysis of the composition of the rhizosheath and root microbial community under moderate drought,it was found that the relative abundance of Bacillus,Dyella,and Talaromyces in the roots and rhizosheath of rice cultivating P.indica is increased.And the relative abundance of Burkholderia,Fusarium,Sarocladium decreased.Bacillus is a beneficial bacterium,and its abundance can promote root growth and rhizosheath formation.The phytopathogenic fungus Fusarium can hinder plant growth,and its abundance decline conducive to root growth and rhizosheath formation.4.Under water stress,P.indica was mainly involved in the regulation of metabolic pathways in rice roots,which might also contribute to root length growth and rhizosheath formation.The colonization of P.indica had a great influence on the genes related to metabolism metabolic pathway in rice.P.indica induced up-regulation biosynthesis of other secondary metabolites related genes,such as genes of acetylajmalan esterase and?-glucosidase,and down-regulation of metabolism of terpenoids and polyketides related genes.Under moderate drought,after rice colonizetion of the P.indica,the genes of the root such as peroxidase and aldehyde dehydrogenase were up-regulated,and the genes such as momilactone A synthase-like and stemar-13-ene synthase are down-regulated.Among them,peroxidase and aldehyde dehydrogenase can reduce the accumulation of peroxides and aldehydes in plants,which is beneficial to plants to cope with stress.Changes in the expression of these genes might contribute to root growth and rhizosheath formation.In summary,this paper established the colonization system of P.indica and rice.It was found that P.indica can promote the formation of rice rhizosheath under water stress.The main reasons were:(1)P.indica might increase root growth by regulating root proton secretion,thereby promoted rhizosheath formation.(2)The colonization of P.indica in rice changed the microbial community structure in rhizosheath and root,increased the abundance of Bacillus,and reduced the abundance of Fusarium in rhizosheath and root,which might contribute to root growth and the formation of rhizosheath.(3)P.indica was mainly involved in regulating metabolic pathways in rice roots,which might also contribute to root length growth and rhizosheath formation.In conclusion,the formation of rhizosheath under water stress is conducive to the efficient use of soil moisture in rice,and the analysis of rhizosheath construction can provide theoretical basis and control methods for the cultivation of water-saving and drought-resistant rice varieties.