Poster: Tropisms
Abs #
406: A cytochrome P450 may be involved in gravitropic signal transduction
The gravity persistent signal1 (gps1) mutant of Arabidopsis has an abnormal response in inflorescence stems when gravistimulated at 4ºC. A wildtype inflorescence stem gravistimulated at 4ºC will not bend. Once returned to vertical at room temperature, the stem will bend in response to the 4ºC treatment. However, the inflorescence stems of gps1 do not respond once returned to room temperature even though they bend normally to constant gravistimulation at room temperature. gps1 was selected from a mutant population generated by T-DNA insertional mutagenesis, and cloning strategies based on the insertion have been employed to identify the gene disrupted. GPS1 has been cloned using thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR). Nested primers were designed based on the T-DNA sequence and used with a degenerate primer to amplify the regions flanking the left border sequence of gps1. Sequence analysis indicated that GPS1 corresponds to At3g20130 identifying it as CYP705A22, a cytochrome P450 of unknown function. CYP705A22 contains all the conserved structures indicative of P450 proteins, including a membrane targeting segment that suggest the protein is associated either with the secretory pathway or plastids. A data mining experiment has identified a family member that is significantly increased in roots during gravistimulation. CYP705A22 was identified using a screen of inflorescence stems and appears not to function in the roots during gravistimulation, however, CYP705A5 does increase significantly and specifically in roots within 5 minutes after gravistmulation. Further analysis of these genes may give insight into the functional significance of cytrochrome P450s in the gravity signal transduction pathway.(Supported by NAG2-1608 from NASA)
