Study Of Thermotolerance In Arabidopsis Atg7 Fes1a Double Mutants And Analysis Of Co-transcription Of Fes1A And Brf2

At Fes1A is a co-chaperone of HSP70.Knocking out Fes1A leads to the heat-sensitive phenotype of Arabidopsis thaliana.The double mutant of atg7 fes1a decreased the sensitivity,compared to fes1a.In this study,the author determined the hypocotyl re-growth of atg7 fes1a and fes1a after a heat stress.The result indicated that the mutation of ATG7 reduced the thermo-sensitivity of fes1a.Western-blotting analysis showed that there was no significant difference in the expression levels of HSP70 and HSP101 between atg7 fes1a and fes1a.No difference in the renaturation rate of heat-denatured(Photinus pyralis)luciferase between atg7 fes1a and fes1a was found,either.To further investigate the cause of the decrase in thermo-sensitivity of double mutant atg7 fes1a,we bred the atg7 hot1 double mutant.As a result,we found that there was no difference in heat-sensitivity between atg7 hot1 and hot1.Basing on the differential expression genes in the transcriptome between atg7 fes1a and fes1a,the author found that two IAA synthesis-related genes were significantly up-regulated in the double mutant of atg7 fes1a,compared to fes1a.These two genes encode the aldehyde oxidase gene(AAO1)and the acetonitrile hydrolase gene(NIT2),respectively.The former oxidizes indole acetaldehyde(IAD)to indole acetic acid(IAA)in the IPA pathway and the latter converts hydrazine indole acetonitrile(IAN)to indole acetic acid(IAA)in the IAOX pathway.We re-evaluated the acquired thermotolerance assays of atg7 fes1a and fes1a when exogenous IAA was applied.As a result,IAA did decrased the heat sensitivity of atg7 fes1a and fes1a.Briefly,up-regulation of AAO1 and NIT2 in IAA synthesis-related pathway was suggested being associated with a decrease in the sensitivity of atg7 fes1a,compared to fes1a.It also reveals that IAA can affect the heat tolerance of plants and the autophagy is related to the synthesis of IAA.There is a phenomenon of co-transcription between the two genes Fes1A and Brf2.In this study,the author constructed the Pro _Fes1A-Fes1A_genomic-Space-Brf2_5'UTR-GUS-p BI121recombinant vector and transformed fes1a.The homozygous transgenic lines were obtained and uesd for the acquired thermotolerance assays.It was found that the heat sensitive defect of fes1a was remedied due to complement expression of Fes1A.Both histochemical staining and Western-blotting showed that both GUS and Fes1A were induced by high temperature.The full co-transcript of about 3400 bp including Fes1A c DNA,the genomic interval sequence(Space)and GUS c DNA was amplified by RT-PCR.To determine whether the genomic interval sequence(Space)between Fes1A and Brf2 had activity of a promoter or not,we constructd the Space-GUS-p BI101 recombinant vector and transformed it into arabidopsis.Histochemical staining results indicated that the genomic interval sequence(Space)had no promoter activity.All results support the conclusion that there is co-transcription between Fes1A and Brf2.It also reveals that there is phenomenon of co-transcription in plants.