Isolation of a Brassica napus L. cDNA encoding a putative high-mobility-group HMG I/Y protein

A cDNA encoding a high-mobility-group protein has been isolated from a microspore-specific library of Brassica napus. The 930 bp cDNA contains a 612 bp open reading frame encoding a protein of 203 amino acids residues exhibiting significant homology to HMG-I/Y protein from Arabidopsis thaliana (62%). The predicted protein contains four copies of the 'AT-hook' motif which is involved in binding A/T-rich DNA. Southern blotting indicates that the HMG-I/Y gene is a single-copy gene in B. napus. Transcription of the HMG-I/Y gene was detected in all tissues examined, with the highest expression in pollen-derived embryos. In situ localization studies of flower organs indicate the transcript to be preferentially located in petals and sepals. Subcellular localization analysis performed during pollen development showed that the transcript of the HMG-I/Y gene is predominantly associated with polysomes.