Effects Of Piriformospora Indica On The Growth,Disease Resistance And Snakin Gene Expression In Banana

Banana(Musa spp.)is the largest trade fruit and one of the most important cash crops of the world,and its economic value is very high.Fusarium wilt of banana is the most devastating banana disease threatening the whole banana industry.However,up to now,no effective cure method has been found for this disease.Snakin is a new class of antimicrobial peptides with broad spectrum stress response activities to both biotic and antibiotic stresses.It was also confirmed to play important roles in promoting plant growth and development and inducing plant disease resistance.Interestingly,in our previous study,several banana snakin genes was found to be induced by Foc TR4 infection,suggesting that Snakin may function in response to banana wilt infection.Pirifomosporra indica,a mycoorrhiza-like fungus,has been proved to play important roles in promoting plant growth and development and stress(both biotic and abiotic stresses)resistance in many kinds of plants.Unfortunately,the use of P.indica in banana plants has not been reported.The colonization of P.indica in plant roots will influence the expression of GA metabolic and signaling related genes.Notably,Snakins belongs to the GASA gene superfamily whose expression can be significantly induced by GA treatment,suggesting that P.indica may also contribute to the regulation of these genes and play role in banana disease resistance.So,in the present study,to explore the effects of P.indica on banana growth and Fusarium wilt resistance,we compared the growth ability,Fusarium wilt resistance and the expression of Snakin genes between the P.indica colonized and normal banana plants.Results generated in this study could be helpful for the understanding of the effects of P.indica on banana growth and resistance and can be provide theoretical basis for its use in plant industry.Results are listed as follows:1.By using Tianbao banana,Fuzhoufenjiao No.1,Sanming wild banana and Fuzhoubajiao as plant materials,we studied the effects of P.indica on the growth of both tissue-cultured banana seedlings and 20 cm-tall big seedlings by using different P.indica inoculation methods.Results showed that P.indica clonoization could improve rooting of tissue-cultured seedlings of all the 4 banana germplasms although the promoting effect varied among different banana germplasms.2.To evaluate the effects of P.indica on banana Fusarium wilt resistance,Tianbao banana,Fuzhoufenjiao No.1,Sanming wild banana and Fuzhoubajiao seedlings colonized or non-colonized by P.indica were subjected to Foc TR4 inoculation.Interesting,the antioxidant enzyme activities of P.indica the banana seedlings are all higher than the non-colonized controls.Notably,we found that P.indica colonization could delay the symptom appearance of Tianbao banana.Results generated in this part indicated that P.indica could induce the antioxidant activity and promote the Fusarium wilt resistance of banana.3.The cDNA sequences of seven members of Snakin gene family were respectively cloned from Tianbao banana,Fuzhoufenjiao No.1 and Sanming wild banana.Interestingly,normal sequences of all the 7 snakins could only be isolated from Sanming wild banana,which may be related to its relative higher Fusarium wilt resitance.Bioinformatic analysis result showed that all the Snakin members were basic proteins belonging to the GASA superfamily with GASA domain and signal peptide and transmembrane structure and without helix-coil structures.And all the SN1s were found to be hydrophilic proteins but the SN2 was found to be hydrophobic.4.Quantitative Real-time PCR was applied to study the expression of the 7 Snakin genes in different tissues and different disease stages(healthy,early stage,middle stage and late stage)of Tianbao banana.The expression levels of several Snakin genes were up-regulated in Fusarium wilt diseased pseudostems and roots but not in leaves.The accumulation of snakin genes in infected tissues indicated that they might function in response to Fusarium wilt infection.Moreover,we also compared the expression levels of Snakins between P.indica colonized and non-colonized controls,and significant or very significant differences were identified.By comparing the Snakin expression levels in Fusarium wilt infected P.indica colonized and non-colonized Tianbaojiao banana,we found significant differences between the two groups,indicating that P.indica might make contribution to banana Fusarium wilt resistance by regulating the expression of Snakin genes.