| The homeodomain leucine zipper(HD-Zip)genes encode transcription factors that have diverse functions in plant development and stress adaptation.The HD-Zip genes are the most abundant group of homeobox genes in plants and do not occur in other eukaryotes.Most HD-Zip genes are broadly expressed in mature plants and seedlings,but others show more organ specific patterns.Here we report a root-specific HD-Zip gene AtHB17.Staining results of gene-GUS reporter lines showed that the expression of AtHB17 transcription factor was root-specific.However,the expression pattern changed in response to salt stress.AtHB17-GFP fusion was used to study the localization of HB17 factor.The subcellular distribution of the green fluorescent signal indicated that the factor was localized in the nucleus.We also found that AtHB17 was upregulated in response to drought,oxidative stress,and exegenous ABA treatments.To investigate further the function of AtHB17,we generated and analyzed the knockout mutant(KO)and the overexpression lines(OX).Our results showed that the knockout mutant was salt sensitive.A functional complementation test was perfomanced,which confirming that the gene was responsible for the salt-sensitive phenotype.The overexpression lines were found more tolerant to salt stress,drought,and oxidative stress compared with the wild type plants.To understand how AtHB17 functions to confer the stress-tloerance phenotype,we compared the transcriptome between the wild type,knockout mutant,and overexpression line by using massive sequencing and revealed possible underlying molecular mechanisms.Based on our results,we constructed a working model of AtHB17-mediated stress tolerance.In addition,we generated and analyzed the transgenic tobacco lines overexpressing the AtHB17.Our results showed that overexpression of AtHB17 in transgenic tobacco plants also improved their tolerance to salt and drought stress,indicating that AtHB17-mediated stress tolerance might be conserved in different plant species. |
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