Isolation and characterization of cDNAs that encode eleven small GTP-binding proteins from Pisum sativum

Area of Science:

• Plant molecular biology
• Molecular genetics
• Biochemistry

Background:

• Small GTP-binding proteins are essential molecular switches in cellular signaling pathways.
• Ras-related proteins play critical roles in various biological processes, including cell growth and differentiation.
• Understanding plant-specific GTP-binding proteins is key to deciphering plant development and stress responses.

Purpose of the Study:

• To isolate and characterize novel ras-related small GTP-binding protein cDNAs from pea (Pisum sativum).
• To investigate the structural and phylogenetic relationships among these identified proteins.
• To examine the gene expression patterns of these cDNAs in different pea tissues.

Main Methods:

• cDNA library screening from pea leaves.
• Amino acid sequence analysis and comparison.
• Phylogenetic analysis using established GTP-binding protein families.
• GTP-binding activity assay of expressed protein.
• RNA gel blot analysis for gene expression profiling.

Main Results:

• Eleven cDNA clones (pra1-pra9C) encoding 22-25 kDa proteins with 45-92% amino acid identity were isolated.
• Proteins possess conserved GTP/GDP-binding domains, an effector domain, and COOH-terminal cysteine residues.
• Expressed pra6 protein demonstrated GTP-binding activity.
• Phylogenetic analysis revealed two subgroups related to YPT/rab families (ypt3/rab11-like and YPT1/rab1-like).
• Differential gene expression was observed in pea leaves and roots, with variations among related genes.

Conclusions:

• The study identified a novel family of pea ras-related small GTP-binding proteins.
• These proteins are structurally diverse and phylogenetically classified into distinct subgroups.
• Differential expression patterns suggest tissue-specific roles for these GTP-binding proteins in pea plants.