Identification And Function Analysis Of GhWRKY41,a Novel WRKY Gene From Cotton (Gossypium Hirsutum L.)

During their life span, plants must confront various biotic and abiotic stresses. Among these, drought and salt, which decrease the availability of water to the plant cell, are primary limiting factors of plant growth, development and crop yield and quality. To cope with these environmental stresses, plants have evolved intricate adaptive strategies to help avoid or tolerate cellular dehydration. Transcription factors play pivotal roles in this progress. WRKY is a recently discovered superfamily of transcription factors existing abroad in plants. It regulates downstream gene expression mainly by binding to W-box present in promoter of target genes. According to previous reports, WRKY proteins are involved in multiple biotic/abiotic stress responses and development and physiological processes.Currently, their roles in biotic stress tolerance are very thorough. Little information is known about their function machanism in abiotic stress tolerance especially in non-model plants. Cotton is planted all over the world; its role as a significant source of fiber, oil and biofuel products makes it an important cash crop worldwide. Here, we isolated a group III WRKY gene, GhWRKY41, from cotton (G. hirsutum L.) and characterized its sequence feature, expression pattern and function by qPCR, histochemical staining and analysis of enzyme activity. The main results are as follows:(1) The full-length cDNA sequence is1274bp including1038bp open reading frame (ORF) which encodes a355-amino acid protein with a predicted molecular mass of40kDa and an isoelectric point of5.42. A protein sequence comparison with DNAMAN demonstrated that GhWRKY41shared high homology with other group III WRKY proteins. Phylogenetic analysis demonstrated that GhWRKY41was closely related to group III WRKY family members from other plants.(2) A1,204-bp fragment of the GhWRKY41promoter was isolated by hiTail-PCR method. PlantCARE and PLACE databases analysis showed that various cis-acting elements associated with tissue specific expression, abiotic stress, biotic stress, and development were identified.(3) The GhWRKY41protein localized in the nucleus and can transactivate the expression of both the reporter genes HIS3and ADE2in yeast, suggesting that GhWRKY41functions as a transcriptional activator.(4) qPCR revealed that the expression of GhWRKY41can be induced by abiotic stress, including drough, salt, cold and heat. In addition, signaling molecules such as ABA and H2O2also could up-regulate the GhWRKY41transcription.(5) Overepression of GhWRKY41enhances plant tolerance to drought and salt stress. stomata closure was enhanced in GhWWRKY41-overexpression plants under osmotic stress. GUS staining showed that GhWRKY41specific expressed in guard cell under osmotic stress treatment. Many cis-acting elements involved in ABA signalling present in promoter of GhWRKY41. These results indicated that GhWRKY41enhances plant tolerance to drought and salt stress in an ABA-dependent manner.(6) Under drought and salt stress, transgenic plants exhibited low ROS content. Activities of antioxidant enzymes, including SOD, POD, CAT and APX in transgenic lines were higher than those in wild type plants, suggesting that GhWRKY41enhances response to drought and salt stress through the control of cellular ROS production.