The Study On Identification And Characterisitics For Small GTPase Gene Family Of Populus Trichocarpa

Small GTPase proteins exist in biology widely, including:yeast, animals and plants, This super family is structurally and functionally classified into at least five families:Ras, Rho, Rab, Sarl/Arf and Ran. However, plants contain only Rab, Rho, Arf and Ran homolog. Small GTPase proteins play a pivotal role as important molecular switches, containing four guanine nucleotide (GTP/GDP) binding (GNB) domains and an effectors domain. Small GTPase proteins regulate many cell activities, such as cell signaling transduction, cell proliferation, cytoskeleton restructuring, cellular vesicular transportation and gene expression, etc. Our study researches the Populus trichocarpa small GTPase genes expression pattern and its response to different stress conditions.There are114small GTP members in the genome of P. Trichocarpa by the homologous searches,92small GTPase protein genes are located on chromosomes; the others are located on the scaffold. Evolutionary tree analysis shows that small GTP protein genes in Populus trichocarpa are also classified into four subfamilies, which is similar to the Arabidopsis thaliana small GTPase protein gene classification, though there are twenty-one more members in the P. Trichocarpa, including nine in the Rab subfamily, ten in the Arf subfamily, two in the Rop subfamily. Through the domain analysis, all the Populus trichocarpa small GTPase proteins have the conserved domain in the plant small GTPase, especially, the members in the same subfamily share high homology in protein and gene structure. The number of the Populus trichocarpa small GTPase reaches114by the chromosomes replication, resulting in the small GTPase family augments.Half quantitative RT-PCR analysis indicates36genes express in eight parts in the plant organization, and some of them specifically express in certain part. This result demonstrates that the Populus trichocarpa small GTPase genes expression pattern has the tissue specific and function redundancy characteristics. Numerous small GTPase genes respond to stress conditions. Under different stress conditions, their expression pattern changes, some increase and others decrease. Through the analysis of promoter sequence of GTPase small protein gene family in Populus trichocarpa, we show that small GTPase protein genes in Populus trichocarpa have response to the listed14related components. Combined with the result of small GTPase protein genes such as PtRabF2a、PtRabAlc、PtRabB1b、PtRabD2c、 PtRabF1b、PtRabA1a、PtRabA6、PtRabH1d、PtRop6、PtRop10、PtRop11、PtArfC1e expression pattern response to different stress conditions, small G protein genes indeed respond to stress and hormone disposal, and actually, we do find some components in the promoter sequence of these small GTPase genes.