Cloning And Preliminary Functional Study On Thermotolerance Of Distinct Transcripts Variants Of Maize Gene ZmHsf23

Maize is an important Gramineous food and cash crop.It often suffers from biotic and abiotic stresses during growth.Heat shock transcription factors(HSFs)are highly conserved in plants,involving in a variety of abiotic stress responses.At present,there are few reports on maize Hsfs.Here we observed that ZmHsf23 could be quickly and highly induced by heat stress.Based on these results,we cloned the two transcripts of ZmHsf23 and named them as ZmHsf231 and ZmHsf23 Ⅱ.Here are some analysis results.1.Through sequence conservation analysis and phylogenetic tree construction,we found that ZmHsf23 has high homology with the HsfA6 family of Gramineous plants.The full length of ZmHsf23 Ⅰ CDS was 1098 bp,encoding 365 amino acids.The full length of ZmHsf23 Ⅱ CDS was 1053 bp,encoding 350 amino acids.Compared with ZmHSF23 Ⅰ,15 amino acids were absent in the DNA binding domain(DBD)of ZmHSF23 Ⅱ.2.Analysis of tissue expression patterns showed that the expression of ZmHsf23 transcripts were extremely low in each tissue in normal-grown maize plants.Both of the two transcripts were rapidly induced by heat shock and ABA induction.ZmHsj23 Ⅰ has a higher expression level than ZmHsf23 Ⅱ.3.Subcellular localization analysis showed that both ZmHSF23 Ⅰ and ZmHSF23 Ⅱ were localized in the nucleus.4.Analysis of yeast self-activation activity activity confirmed that ZmHSF23 Ⅱ has transcription activity in yeast cells,while ZmHSF23 I has no transcription activity,which indicated that the extra 15 amino acids might be response for the loss of transcription activity in ZmHSF23 Ⅰ.5.We found that ZmHsj23 Ⅱ-overexpressing transgenic Arabidopsis lines have significantly higher survival rates than wild type under heat stress,while no survival rates differences could be observed between ZmHsj23 Ⅰ-overexpressing transgenic lines and wild type.Expression analysis showed that the expression level of heat shock-related genes in ZmHsf23 Ⅱ transgenic Arabidopsis increased after heat treatment,and were higher than that in wild type plants.But these genes were not significantly different from wild type plants in ZmHsf23 Ⅰ transgenic Arabidopsis.6.Compared with wild type,ZmHsf23 Ⅱ-overexpressing transgenic Arabidopsis lines was more sensitive to ABA,while it is not sensitive between ZmHsf23 Ⅰ-overexpressing transgenic lines and wild type.Expression analysis showed that the expression level of stress-related genes were not significantly different in wild type plants and both two transcripts of ZmHsf23 transgenic Arabidopsis after heat.7.Arabidopsis thaliana ascorbate peroxidase gene AtAPX2 is significantly up-regulated in ZmHsf23 Ⅱ overexpressing transgenic Arabidopsis thaliana after heat shock treatment than wild type.It is hypothesized that ZmHsf23 Ⅱ may be involved in its metabolic pathway.