DIFFERENTIAL ACCUMULATION OF 2 GLYCINE-RICH PROTEINS DURING COLD-ACCLIMATION ALFALFA

Two mRNAs, MsaCiA and MsaCiB, encoding for proteins harboring glycine- rich motifs, accumulate in alfalfa during cold acclimation. Fusion pol ypeptides containing the amino acid sequences deduced from these mRNAs were produced in Escherichia coli and used to raise antibodies. Each antibody cross-reacted specifically with soluble polypeptides, MSACIA- 32 and MSACIB, respectively. These polypeptides were detectable only i n crowns of cold-acclimated plants, even though MsaCiA mRNA accumulate d in both crows and leaves during cold acclimation. The analysis of pa rietal proteins showed that several MSACIA-related proteins, with a mo lecular mass of 32, 41 and 68 kDa, did accumulate in leaf cell walls a nd one of 59 kDa crown cell walls. This diversity is most probably due to a tissue-specific maturation of MSACIA. A discrepancy was found be tween the time-course of accumulation of MSACIB and the one of the cor responding transcript. These results indicate that timing and localiza tion of MSACIA and MSACIB expression are different, and suggest that t his differential expression involves both transcriptional and post-tra nscriptional events. Comparisons made among six cultivars of contrasti ng freezing tolerance suggest that low tolerance could be explained by failure to accumulate proteins like MSACIA and MSACIB at a sufficient level.