Abstract
Two-dimensional electrophoresis, coupled with MALDI-TOF-MS, was used to identify differentially expressed proteins between young and mature leaves of sweet potato [Ipomoea batatas (L.) Lam]. The results showed that there were 25 differential proteins between young and mature leaves. The Rubisco activase (RCA) that catalyzes the activation of Rubisco in vivo and plays a crucial role in photosynthesis was among these 25 proteins. So far, little was known about the molecular biology of RCA in sweet potato. Here, this research reports the cloning and characterization of two genes encoding the short isoform and the long isoform of sweet potato RCAs. Analysis of DNA sequences of RCA suggested that the corresponding mRNAs were transcribed from two different genes. To study the roles of these two RCA isoforms in photosynthesis, we investigated the expression patterns of these RCA genes at the mRNA and protein levels every 2 h in a photoperiod and under different temperatures conditions. The results indicated that these two RCA isoforms may play different roles in regulating photosynthesis and they may be regulated by light, heat or both. In addition, there were interactions between Rubisco large subunit (RBCl) and short isoform RCA (RCAs) as well as RCAs and long isoform RCA (RCAl), but no interaction between RBCl and RCAl, implying they might form a sandwich-like structure (RBCl–RCAs–RCAl), at least in yeast cells. These results provided new information on the modulation of RCA genes in sweet potato, which could be useful in improving photosynthesis and plant growth in sweet potato.Electronic supplementary materialThe online version of this article (doi:10.1007/s11033-013-2744-7) contains supplementary material, which is available to authorized users.
Highlights
Sweet potato is the sixth most important crop for food and industrial materials worldwide after rice, wheat, potato, maize and barley, and it is the fifth most important crop in many developing countries
The Rubisco activase (RCA) that catalyzes the activation of Rubisco in vivo and plays a crucial role in photosynthesis was among these 25 proteins
There were interactions between Rubisco large subunit (RBCl) and short isoform RCA (RCAs) as well as RCAs and long isoform RCA (RCAl), but no interaction between RBCl and RCAl, implying they might form a sandwich-like structure (RBCl–RCAs–RCAl), at least in yeast cells. These results provided new information on the modulation of RCA genes in sweet potato, which could be useful in improving photosynthesis and plant growth in sweet potato
Summary
Sweet potato is the sixth most important crop for food and industrial materials worldwide after rice, wheat, potato, maize and barley, and it is the fifth most important crop in many developing countries (http://cipotato.org/sweetpotato/ facts and http://www.fao.org/). Sweet potato can be grown in areas that are not suitable for corn (a major crop for ethanol production in some countries) and yields 30 % more starch than corn [5]. More and more studies on sweet potato are focused on increasing biomass production by improving photosynthesis. Rubisco exists in three states in photosynthetic cells: (1) inactive form (type E); (2) inactive form of carbamylation (type EC); (3) active form (type ECM). The proportion of these Rubisco forms directly influences photosynthesis in plants [10,11,12]. For transgenic plants expressing anti-RCA gene, the RCA content and Rubisco activity were all decreased, and their photosynthesis was reduced dramatically. After heatstress at 42 °C, compared with the transgenic plants expressing anti-RCA gene, the photosynthesis of wild-type plants was recovered completely in a short time, while antisense plants only slightly recovered [16, 17]
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