Functions of SAUR Genes in Auxin Response
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Auxin regulates many aspects of plant growth and development. The major natural auxin found in plant is Indole aceticacid (IAA). Auxin regulates plant growth and development through modulation of gene expression that is achieved through the degradation of a group of repressor proteins known as Aux/IAA proteins. There are 3 known gene families that are immediately induced by auxin. They are SAUR, Aux/IAA, and GH3. The SAUR gene family consists of over 70 genes that are belong to several clusters depending on their sequence homology. While exact functions of SAUR genes are not known, depending on the predicted protein sequences, several possible functions have been suggested. In an attempt to study the functions of SAUR genes, we cloned several members of SAUR gene family (At5g10990, At1g75590, At1g19840, At4g34750, and At2g28085) from Arabidopsis. All these clones contain N-terminal calmodulin binding domains. Additionally, we constructed C-terminal myc tagged version of these genes and expressed in E. coli. Using in-vitro studies we demonstrated that these proteins are rapidly degraded in plant extracts. We have also generated transgenic Arabidopsis plants with SAUR-myc and SAUR-GUS gene constructs that can be used for in-vivo experiments. Moreover, truncated SAUR gene constructs (without calmodulin binding domain) were generated. Transgenic Arabidopsis plants with these constructs have been selected for further study.