RESUMO
Ras super family proteins serve as molecular switches regulating many different cellular processes. However, given the large number of family members, sequence information has provided little insight into the function of individual proteins. This study examined phenotypic alterations in an Arabidopsis ara2 mutant, in which a Ras super family member-encoding gene is disrupted by a T-DNA insertion. Although one mutant line (Salk_013811) was hypersensitive to auxin, its T-DNA insertion was in the 5'-UTR of ARA2. Thus, we examined a true ARA2 knock-out mutant (Salk_077747) which contains an insertion in the first exon of ARA2. We found that ARA2 expression is responsive to auxin and at low concentrations, ara2 mutant plants exhibit increased numbers of lateral roots. ARA2 overexpression causes plants to exhibit hypersensitivity to auxin, due to altered expression of auxin-responsive genes, and these plants exhibited reduced numbers of lateral roots. A GFP-ARA2 fusion protein localized to the endosomes, suggesting that ARA2 may play a role in vesicle trafficking of components involved in polar auxin transport. Taken together, these results show that ARA2 is an essential component of a pathway that couples auxin signaling to plant growth and development.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/crescimento & desenvolvimento , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , DNA Bacteriano , Regulação da Expressão Gênica de Plantas , Teste de Complementação Genética , Mutagênese Insercional , Mutação , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas/metabolismo , RNA de Plantas/genéticaRESUMO
Expansins are cell wall loosening proteins that appear to permit the microfibril matrix network to slide in growing plant cell walls, thereby enabling the wall to expand. To scrutinize possible impacts on plant growth and development when expansins are over-expressed, we characterized phenotypic alterations of the transgenic plants that constitutively expressed AtEXP3 or AtEXP-beta1 under control of 35S-CaMV promoter. Our results suggest that both AtEXP3-OX and AtXPbeta1-OX are very sensitive to salt stress. However, the mechanisms underlying their enhanced salt sensitivity appear to be different.