Functional Analysis Of Trihelix Transcription Factor Genes In Tomato Disease Resistance Responses

Trihelix transcription factors,also known as GT factors,are a group of plants-specific transcriptional factors.Recent studies have found that Trihelix transcription factors play important role in regulating plant table fur morphogenesis,embryo and seed development,petal differentiation and responses to a variety of environmental abiotic stress.However,little is known about the involvement of Trihelix transcriptional factors in plant disease resistance.In the present study,I cloned and identified 27 Trihelix transcription factor genes from tomato and studied by using virus-induced gene silencing(VIGS)approach to explore their possible involvement in disease resistance to Botrytis cinerea and Pseudomonas syringae pv.tomato DC3000(Pst DC3000).(1)Bioinformatics analysis identified a total of 36 genes coding for Tirhelix transcriptional factors in tomato genomes.Twenty-seven trihelix genes were cloned and identified,and 23 of them were chosen for future study.Most of the Trihelix transcriptional factor proteins contain at least one Myb DNA binding domain.(2)Quantitative real-time PCR analysis indicated that transcription levels of Trihelix transcription factor genes were induced with different patterns after infection by B.cinerea or Pst DC3000.Meanwhile,the expression levels of most of the members were upregulated by one of the two pathogens tested.(3)The possible involvement of the 23 Trihelix transcriptional factor genes in disease resistance was explored by using virus-induced gene silencing mETHod.The results showed that SIGT7,SIGT13,SIGT14 and SIGT15 are involved in regulation of plant in responses to B.cinerea or Pst DC3000.Particularly,SIGT7,SIGT13,SIGT14 and SIGT15 are negative regulators of resistance to B.cinerea.While SIGT7,SlGT13 and SIGT14 were found to be positive regulators of resistance to Pst DC3000,SIGT15 seems to be a negative regulator of resistance against Pst DC3000.(4)Transient overexpression of SlGT7,SlGT13 or SlGT14 led to programmed cell death and induced generation of a large amount of reactive oxygen species in N.benthamiana.Transient overexpression of SIGT15 did not induce programmed cell death but resulted in an increased susceptibility to B.cinerea,indicating that SIGT15 plays a negative role in resistance to B.cinerea.(6)Expression of genes encoding antioxidant enzymes was induced in SIGT7,SIGT14 or SlGT15-silenced plants.Expression levels of JA/ETH-responsive PR genes were upregulated while the expression of SA-responsive PR genes was downregulated in SlGT7/SlGT14-silenced plants.However,both of the JA/ETH-responsive and SA-responsive PR genes were upregulated in SIGT15-silenced plants.(7)ROS in SlGT7/SlGT13/SIGT14/SlGT15-silenced plants were detected by Lumino chemiluminescence method.Data showed that both C08-and flg22-induced ROS burst was observed within 10 minutes after addition of the elicitor in SlGT14-or SlGT15-silenced plants.Taken together,our results indicate that SIGT7,SlGT13,SIGT14 and SIGT15 play important roles in disease resistance against B.cinerea and Pst DC3000.Furthermore,SIGT14 and SIGT15 are probably also involved in PTI.