OsABT,a Rice WD40 Domain-Containing Protein,Is Involved in Abiotic Stress Tolerance

Plant growth and crop productivity are severely affected by abiotic stress on a global scale.WD40 repeat-containing proteins play a significant role in the development and environmental adaptation of eukaryotes.In this study,OsABT,a stress response gene,was cloned from rice(Oryza sativa L.cv.Nipponbare).OsABT encodes a protein containing seven WD40 domains.Expression analysis revealed that the OsABT gene was first up-regulated and then down-regulated following treatment with abscisic acid(ABA)and NaCl,but was down-regulated when treated with PEG8000.Subcellular localization results showed that OsABT was located in the cytoplasm and nucleus of Arabidopsis roots.OsABT transgenic Arabidopsis showed significantly increased tolerance to ABA and salt stress during plant seedling development.However,the transgenic lines were more sensitive to drought stress.Moreover,OsABT can interact with OsABI2,a component of ABA signaling pathway.These results showed that OsABT plays a positive regulatory role in response to salt stress and a negative role in response to drought stress in Arabidopsis.

An Artemisia WD40-Repeat Gene Regulates Multiple Cellular Functions in Arabidopsis

In this study, we isolated a WD40-repeat gene from Artemisia annua glandular trichomes. This gene shows 69.97% sequence similarity to Arabidopsis TTG1 at aminoacid level. Sub-cellular localization study shows that AaWD40 protein diffuses in both cell nucleus and cytosol. The correct nuclear localization of AaWD40 was observed when co-expressed with AabHLH, a putative A. thaliana AtTTG1 homologue cloned from Artemisia annua glandular trichomes. When AaWD40 gene was ectopically over expressed in Arabidopsis transparent testa glabrous1-1 (ttg1-1) mutants of A. thaliana, PAs production in seeds was restored, and the trichomeless phenotypes of mutant were rescued. Real-time PCR analysis results revealed that ETC1, CPC, TTG2 and BAN (the downstream targets of AtTTG1 depend on regulatory complex), which regulate the epidermal differentiation and anthocyanin biosynthesis were differentially expressed as a result of AaWD40 over expression. Furthermore, the CLV1, CLV2, CLV3 and WUS, which are required to maintain the stem-cell niche of Arabidopsis shoot apex, were also modulated by AaWD40 and Arabidopsis TTG1. The transcriptions of AP2/ERF, bHLH, MYB, WRKY and NACs family proteins, which are mostly involved in defense, stress response and development regulation, were remarkably modulated by AaWD40 over expression. We hypothesize that WD40 repeat proteins act as a crucial factor in regulating a wide variety of cellular functions in A. thaliana.