| Description: | Microarray is a powerful tool to examine global transcriptional profiles (TF). If a mutation in a transcriptional regulator results in altered phenotypes, there should be differences in TF,implying downstream events of the mutation. Axr3 mutants are pleotropic semi-dominant mutants which encode a modified Aux/IAA protein (IAA17), a transcriptional regulator. The axr3-1 allele is a P to L change caused by a base substitution in conserved domain II and leads to a severe phenotype. The phenotype of the root of axr3-1 (Co) is shortened with loss of gravitropism, and is less sensitive to auxin by 500 fold. An intragenetic suppressor (revertant) of axr3-1, axr3-1 R4, shows the WT-like phenotype. A single base change in the axr3-1 R4 allele within conserved domain IV results in replacement of half of domain IV with 37 new amino acids.Protein-protein interaction between Aux/IAA and ARF (a transcription factor) is suggested as a regulatory mechanism in auxin-responsive plant growth and development. To answer the question, how a mutation within domain II causes a severe phenotype and how an additional mutation within domain IV of axr3-1 causes phenotypic reversion, protein-protein interactions were examined in a yeast two-hybrid system. IAA17 and axr3-1 proteins interacted with each other, ARF and other Aux/IAA proteins. However, axr3-1R4 protein did not interact with ARF or other Aux/IAA proteins.Much research in auxin signaling has been conducted on Aux/IAA proteins, but little is known about downstream events. Downstream genes of Aux/IAA proteins potentially can be identified with this mutant. Its identical genetic background as WT except for the mutation and its severe phenotype predict differences in TF between WT and axr3-1, implying genes involved in the phenotype associated possibly with events related to downstream IAA17. In addition, examination of the TF between WT and the revertant should provide mechanistic information of IAA17 protein-protein interactions. If the TF are the same between WT and revertant, the importance of domains III/IV is verified and suggests that the protein is a negative regulator; if not, the involvement of additional downstream genes in the phenotypic reversion is indicated. Identifying a downstream gene(s) will contribute to understanding of auxin biology and plant growth.RNA will be extracted from the roots of WT, axr3-1, and the revertant grown for one week under light:dark cycle. |
NASCArrays Information at The BAR
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