Abstract:

We identified two cDNAs (designated as GhHyPRP1 and GhHyPRP2) encoding putative cell wall hybrid proline-rich proteins (HyPRPs) from cotton (Gossypium hirsutum) ovule and fiber cDNA libraries. GhHyPRP1 and GhHyPRP2 encode 327 and 137 amino acids, respectively. Both GhHyPRP1 and GhHyPRP2 proteins have the same overall primary structure: an amino-terminal signal peptide; a central proline-rich domain that contains nine copies of 13 peptide repeat for GhHyPRP1 (similar to PPTYAPPPKSPSK), and 10 copies of double peptide repeat for GhHyPRP2 (similar to CP); and a carboxy-terminal nonrepetitive domain with a certain number and specific distribution of cysteines which is in GhHyPRP1 six cysteines and a typical eight-cysteine motif (8 CM) in GhHyPRP2. Based on the protein domain organization and protein similarity, GhHyPRP1 was grouped into the HyPRP class A proteins, while GhHyPRP2 into the HyPRP class B proteins of higher plants. Phylogenetic relationship alalysis clearly showed that GhHyPRP1 and GhHyPRP2 were separated into two subgroups, in the top of different clade respectively, demonstrating that they were evolutionally far related which are consistent with the results based on protein domain organization and protein similarity analysis. Expression analysis of the two GhHyPRPs was carried out by quantitative realtime RT-PCR. The results showed that GhHyPRP1 was highly expressed in hypocotyls, while GhHyPRP2 expressed preferentially in 10 dpa ovule. The results suggest that GhHyPRP1 and GhHyPRP2 may play a role in the development of different cotton tissues.

Key words: Cotton (Gossypium hirsutum), Hybrid proline-rich protein (HyPRP), Primary structure, Gene expression