Differential expression of three RbcS subfamilies in wheat

The RbcS multigene family in hexaploid wheat, Triticum aestivum, is composed of at least 22 genes that were classified into four subfamilies (SFs). In this study, the relative expression of three SFs was analysed, (I) in various plant organs at different developmental stages of one hexaploid line and two tetraploid lines-a wild and a cultivated one-and (2) in fully expanded flag leaves of 16 diploid, 54 tetraploid, and 40 hexaploid lines. The expression of RbcS genes was found to be tissue-specific (highest expression in leaves and stems) and negatively correlated with organs' age. In all cases-at all ploidy levels, in all plant organs and developmental stages, and in most light treatments-SF-1 genes accounted for at least 80% of the RbcS mRNA. Similar to other plant species, wheat RbcS genes were found to be light regulated, with the expression of SF-I genes being less affected by light than the other two SFs. A negative correlation between the expression level and RFLP was found. Accordingly, the SF with the highest level of expression (SF-I) was the most conserved, suggesting a higher selection pressure for the more active RbcS genes. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.