| Endophytic fungi can promote plant growth and enhance the host’s resistance to biotic and abiotic stresses.They have the potential as a "plant vaccine".Our research team previouly reported an endophytic Fusarium lateritium strain that could promote growth and disease resistance of potato.In this study of tobacco,another solanaceae crop,was used as the target to explored the influence of F.lateritium on growth and disease resistance of tobacco.The virulence factor lipase FLL1 was used as the entry point to construct the fll1 gene knockout and overexpression vector,and obtain the corresponding gene knockout and overexpression strains.In order to clarify the effect of fll1 gene on the strain,the differences of spore production,growth metabolism and spore germination of F.lateritium wild-type,fll1 gene knockout and overexpression strains were detected.In order to clarify the function of fll1 gene in the interaction between F.lateritium and plants,the morphological and physiological indexes of tobacco treated by each strain were counted and the expression of related defense genes was detected.To reveal the function of fll1 gene and provide a theoretical basis for the study of the interaction mechanism between F.lateritium and plants.Reveal the function of FLL1 in the process of interaction with plants.The results are as follows:1.F.lateritium root irrigation treatment promoted the growth of tobacco.In comparison with the control,the leaf surface area,the number of main roots,the number of leaves and the content of chlorophyll a and b of the treated plants increased by 5.0,3.9,1.4 and 1.3 folds respectively.2.Expression of tobacco plant hormone synthesis gene mediated by Fusarium lateritium.In comparison with the control,the expression of phytohormone synthesis related genes in the treated plants was significantly up-regulated(～1.639.9 folds).3.F.lateritium mediated R gene and SA,JA signals enhance tolerance to bacterial wilt of tobacco.After infection with the pathogen of tobacco bacterial wilt,Ralstonia solanacearum,the transcription patterns of the related genes of salicylic acid(SA),jasmonic acid(JA)and R gene signal were analyzed.It was found that the SA and JA related genes were significantly up-regulated in the treated tobacco plants(～1.28.3 folds),while only one R gene was significantly down-regulated(～50%),and the bacterial wilt disease index decreased by about 30%.4.F.lateritium could colonize the tobacco roots.F.lateritium with GFP-labeled was cocultured with tobacco for 12 h,and the green fluorescent hyphae of F.lateritium were detected surrounded the roots of tobacco roots.5.FLL1 of F.lateritium did not affect the polar growth of the strain.There was no significant difference in the growth of Δfll162,Δfll193,fll1OE and WT strains.6.FLL1 was not involved in spore production,but affected spore germination in the early stage.There was no significant difference in the number of spores produced by Δfll162,Δfll193,fll1OE and WT,but it was detected that the spore germination rate of fll1OE at 4 and 5 hours was higher than that of wild-type WT,Δ fll162,Δfll193.7.FLL1 affected chlorophyll synthesis,but did not affect tobacco leaf growth.F.lateritium WT,fll1OE and Δ fll193 strains treated tobacco seedlings respectively,counted the tobacco leaf surface area and detected the chlorophyll content.The results showed that the chlorophyll content of WT strain treatment group was the highest,while the chlorophyll content of Δfl1193 treatment group was higher than that of fll1OE treatment group,but there was no significant difference in leaf surface area between treatment groups.8.FLL1 is involved in the activation of SA and R protein signaling pathways in tobacco.The expression levels of SA and R gene marker genes were detected after F.lateritium WT,fll1OE and Δfll193 strains treated tobacco respectively.The results showed that the activation of R protein and SA defense signal in tobacco was blocked after fll1 gene knockout of F.lateritium. |
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