cDNA cloning and molecular analysis of papaya small GTP-binding protein, pgp1

In the course of papaya EST collection, one clone (pRA4-3) encoding partial sequence of papaya small GTP-binding protein gene, pgp1, was obtained. Based on the sequence information of pRA4-3, the entire coding region of pgp1 was cloned using the 3'RACE PCR technique. ORF of pgp1 is 636bp long and deduced molecular weight of the protein is 23,311. Phylogenetic analysis showed that PGP1 belongs to YPT/RAB group of the small GTP-binding protein and is a homologue of RAB2. Southern analysis showed that there are several pgp1-related genes in papaya genome. Northern analysis showed that pgp1 was expressed equally in stems of seedlings that were grown under light and dark conditions. This result shows that PGP1 is not involved in the phytochrome-mediated signal transduction as an auxin signal transducer in stems of papaya seedlings.