TWO RUBISCO ACTIVASE GENES FROM IPOMOEA BATATAS HAVE DIFFERENT ROLES IN PHOTOSYNTHESIS OF ARABIDOPSIS

Abstract

Rubisco activase (RCA) that functions as a molecular chaperone regulates the activity of the Calvin-Benson cycle via regulation of the Rubisco activity. In plants such as Arabidopsis thaliana, Spinacia oleracea, and Oryza sativa, there are two RCA isoforms from two mRNAs that are produced from alternative splicing of the transcribed pre-mRNA of a single RCA gene. However, this research reported that the transcripts of the two IbRCA isoforms in sweet potato (Ipomoea batatas) were transcribed from two different genes. To study the roles of these two IbRCA isoforms in photosynthesis, we inserted these two IbRCA genes into the genome of Arabidopsis with deletion of RCA gene (ΔRCA), resulting in IbRCAs- and IbRCAl-expressing plants, respectively. Analysis of these transgenic Arabidopsis indicated that the IbRCAs-expressing plants were similar to wild-type plants under ambient CO2 concentration and 22°C conditions, suggesting that expression of IbRCAs gene was sufficient for functional complementation of ΔRCA plants under normal conditions. However, IbRCAsexpressing plants were more susceptible to moderate heat stress (26°C) compared to wild-type plants. In contrast, although the IbRCAl-expressing plants had to grow normally in high CO2 concentration conditions, there were almost no differences in growth and photosynthesis between normally grown and heat-treated plants, implying that IbRCAl-expressing plants had a better heat-resistance than IbRCAs-expressing plants.