Characterization of a Novel RING-Type Ubiquitin E3 Ligase GhRING2 Differentially Expressed in Cotton Fiber

摘要

The ubiquitin-proteasome proteolysis pathway is responsible for the degradation of abnormal and short-lived proteins to regulate many important biochemical activities in eukaryotes. By employing affymetrix microarray analysis, we have identified a novel ubiquitin ligase E3 gene GhRING2 that is differentially expressed between two Gossypium hirsutum lines-Texas Marker-1 (TM-1) and Chromosome Substitution Line CS-B25. The CS-B25 line has chromosome 25 from G. barbadense substituted into TM-1. The complete nucleotide sequences of GhRING2 along with its 5’-flanking region were obtained by genomic walking. GhRING2 was highly expressed in elongating fiber, and GUS expression directed by the GhRING2 promoter was found in hypocotyls and young stems of transgenic Arabidopsis plants. Using a yeast two-hybrid assay GhRING2 was found to interact with a PROTODERMAL FACTOR1 (GhPDF1) protein. GhPDF1 was expressed preferentially in immature ovules and fiber initials, and the GhPDF1 gene had been suggested to play a role in cell fate determination and fiber development. Pull down and plasmid swap assays further confirmed the interaction between GhRING2 and GhPDF1. The expression and protein interaction data indicate that GhRING2 may be involved in the turnover of GhPDF1 and participation in the transition from initiation to elongation stages during fiber development. Our data strongly suggest that the ubiquitin-proteasome pathway may regulate cotton fiber growth and development. The nucleotide sequence data of GhRING2 in this article have been submitted to the Gen Bank Nucleotide Sequence Data Bases under the accession number BankIt 1,742,008 SeqKM 108,000.