The Mechanisms Of Auxin Response Factor ARF6 And IAA23 Interact To Regulate Arbuscular Mycorrhizal Symbiosis In Tomato

Tomato(Solanum lycopersicum)is the vegetable crop with the largest facility cultivation area in China.It has a broad market prospect.However,the problem of reduced utilization of nutrients such as nitrogen(N)and phosphorus(P)is common in production,which severely restricts the sustainable development of the tomato industry.Arbuscular mycorrhiza is a mutually beneficial symbiotic structure formed between arbuscular mycorrhizal fungi(AMF)and plants.It can improve the ability of plants to absorb soil mineral elements,especially the P,through the two-way nutrient exchange between fungi and plants.In addition,arbuscular mycorrhiza also plays an important role in improving plant resistance to stress and improving crop quality and yield.Phytohormones are important signal substances in the process of symbiosis between AMF and plants.A large number of studies have shown that auxin and strigolactones(SLs)are indispensable response factors in the process of arbuscular mycorrhizal formation.Therefore,studying the regulation of phytohormones in the AMF symbiosis process is of great significance for improving the utilization of P elements by plants,reducing the input of P fertilizer and improving the utilization of poor soils.In this paper,using tomatoes as the experimental material,virus-induced gene silencing(VIGS)technology and molecular biology methods are used to explore the influence of auxin signal transduction factors on arbuscular mycorrhizal symbiosis in tomato.The main findings are as follows:1.Clarified the effect of auxin response factor SlARF6 on arbuscular mycorrhizal symbiosis in tomato.The study found that when wild-type tomato was inoculated with AMF under low P conditions,the proportion of hyphae,arbuscule and vesicles in arbuscular mycorrhiza gradually increased with the increase of treatment time,and the arbuscular mycorrhizal specific expression genes BCP1,PT4,and PT5 were also expressed in large amounts in the late period of colonization.The content of auxin and SLs in the roots of tomato in the early stage of colonization increased significantly in the early stage of colonization,which preliminarily proved that auxin and SLs signals played an important role in the early colonization period.According to the change of gene expression,the SlARF6 was significantly up-regulated by AMF was screened out,and the SlARF6 gene was further silenced by VIGS technology,and it was found that SlARF6 negatively regulates the symbiosis process of tomato arbuscular mycorrhiza,and at the same time inhibits the promotion effect of AMF on tomato P absorption.2.Proved the protein interaction relationship between ARF6 and AUX/IAA23 in tomato plants.The study found that some genes in the SlIAA gene family were expressed in large quantities after AMF treatment under low P conditions.The experiment further used Y2 H technology to conduct preliminary screening of AUX/IAA that may interact with tomato ARF6 protein,and then using Bi FC,LCI and GST pull-down technology from a molecular perspective proved that there is an interaction relationship between tomato ARF6 protein and the AUX/IAA23 protein.3.Clarified the effect of auxin /Indole-3-acetic acid protein AUX/IAA23 on the arbuscular mycorrhizal symbiosis in tomato.The SlIAA23 gene silencing plant constructed by VIGS technology was used as research material.The study found that silencing SlIAA23 under low P and AMF inoculation treatments inhibited the symbiosis process of AMF and tomato,and reduced the promotion effect of AMF on tomato P absorption,which preliminarily proved SlIAA23 may be a positive regulator in the process of tomato arbuscular mycorrhizal symbiosis.In addition,the study found that SlARF6 gene silencing significantly enhanced the inducing effect of AMF on the SLs content and the transcription level of synthetic genes CCD7 and CCD8,while the SlIAA23 gene silencing significantly inhibited the inducing effect of AMF on the SLs content and the transcription level of synthetic genes CCD7 and CCD8.In summary,we have preliminarily clarified the effects of ARF6 and AUX/IAA23 on arbuscular mycorrhizal symbiosis in tomato,and determined that ARF6 is an inhibitor of arbuscular mycorrhizal symbiosis,and AUX/IAA23 is a promoting factor.They affect the arbuscular mycorrhizal symbiosis and arbuscular mycorrhiza promoting tomato P absorption by protein interactions,and this process may be achieved by influencing the synthesis of SLs.