Function And Mechanism Analysis Of Transcription Factors TaPIMP1and TaPIEP1in Wheat

Sharp eyespot （primary pathogen Rhizoctonia cerealis） and common root rot （major pathogenBipolaris sorokiniana） have become the major diseases of wheat in China. Drought is the main limitingfactor in the production of wheat all over the world. Transcription factors MYB and ERF play importantroles in plant defense responses to biotic stress and abiotic stresses. Overexpression of certaintranscription factors have been shown to confer enhanced-resistance to certain pathogens in plants. Inorder to understand mechanisms underlaying stress responsesand mine important resistance-relatedgenes in wheat, in our laboratory, two wheat transcription factor genes, TaPIMP1and TaPIEP1werepreviously isolated, and their transformation overexpressing TaPIMP1and TaPIEP1vectors wereconstructed. TaPIMP1and TaPIEP1were respectively transformed into wheat cultivar Yangmai12bybombardment.In this paper, we did the molecular detections and resistancetests on TaPIMP1-overexpressingtransgenic wheat lines in T₂-T₄generations and TaPIEP1-overexpressing transgenic wheat lines in T3-T5generations, and studied the action mechanism of TaPIMP1. The results were as follows:The results of yeast one hydrid and EMSA indicated that TaPIMP1was an activator-typeR2R3-MYB transcription factor. We analyzed8TaPIMP1-overexpressing transgenic lines in T₂-T₄generations by PCR, Southern blot, Q-RT-PCR and Western blot methods. PCR and Southern blotresults showed that TaPIMP1was integraded into the genomes of eight transgenic wheat lines, andcould be heritable. Q-RT-PCR and Western blot results indicated that the mRNA and expression proteinlevels of TaPIMP1were much higher in these8transgenic lines than those in wide-type Yangmai12. Weanalyzed these transgenic plants’ resistance to Bipolaris sorokiniana and droughtstresses. The resultsshowed that the overexpression of TaPIMP1enhanced host resistance to common root rot and droughttolerance in these transgenic wheat plants. And the enhanced-resistance degrees of transgenic wheatlines were positively correlated to the transcriptional and translation levels of TaPIMP1. In order toexplore the mechanism underlying TaPIMP1, we identified defense and stress-related genesupregulated by TaPIMP1by microarray analysis, i.e, PR1a, RD22, TLP4, PR2, GST, GLP, PAL, andDehydrin. The transcript profiles of9defense and stress-relative genes were further assayedbyQ-RT-PCR. The results proved that most of the microarrary resulits were reliable. We also analysed theeffect of plant hormones, ABA, SA, and their inhabitors on TaPIMP1and the9regulatory genes. Theresults indicated that the expression of TaPIMP1and its regulatory genes was induced by ABA and SA.The mechanism underlying TaPIMP1was supposed that TaPIMP1modified positively host responses toB. sorokiniana and drought stressesvia activation of certain defense and stress-related genes in ABA andSA signal pathways in wheat. At the same time, the study also provided resistant germplasm resourcesfor breeding new wheat varieties with resistances to common roor rot and drought.We monitored TaPIEP1-overexpressing transgenic lines in T3-T5generations by PCR, Southernblot, RT-PCR, and Q-RT-PCR techniques. The results showed that introduced TaPIEP1gene intransgenic wheat can be heritable by a single copy or two copes and integrated into7transgenic wheat lines with different genomic loci. The gene TaPIEP1could be overexpressed significantly in transgeniclines, compared with wide type Yangmai12. These TaPIEP1transgenic wheat plantswere inoculated withBipolaris sorokiniana, and Rhizoctonia cerealis, and then subjected to the resistancetests. Resistancetests showed that overexpression of TaPIEP1improved the transgenic wheat lines’ resistance to R.cerealis. Seven transgenic wheat lines also showed enhanced-resistance to Bipolaris sorokinianacompared to wide-type Yangmai12. These results indicated that TaPIEP1could positive regulatewheat’s resistance responses to R. cerealis and B. sorokiniana. This study also provided resistantgermplasm resources for breeding new wheat varieties with resistance to R. cerealis and B. sorokiniana.