Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/2014
Publication Date: 11/12/2014
Citation: Yang, T., Peng, H., Bauchan, G.R. 2014. Functional analysis of calmodulin genes family during tomato fruit development and ripening. Horticulture Research. 1:14057.
Interpretive Summary: Nearly a quarter of all fresh fruits and vegetables in the U.S. market are lost after harvest. Calcium has been shown to be important in controlling fruit ripening and quality. However, the role of calcium-regulated proteins, such as calmodulin, is not clear. This study is to analyze the expressions of six calmodulin genes during tomato fruit development and ripening. The expression of SlCaMs showed an unusual double peak expression pattern. The first flat peak appeared at 10-30 days after anthesis when fruit underwent enlargement. Then their expression levels were declined to the basal level at mature green and breaker stages. Shortly after, a sharp and even higher peak appeared at turning stage. Reducing one calmodulin expression in mature green fruits delayed fruit ripening. These results suggest that calmodulin is required for both fruit size and fruit maturation. This study provides the important information for industry and breeders to manipulate calmodulin level in order to control fruit ripening and improve overall fruit quality.
Technical Abstract: Calmodulin as a ubiquitous calcium sensor can recognize the different developmental and/or stimulus-triggered calcium changes and modulate the functions of its target proteins involved in plant growth and development. However, it remains elusive for the functions of calmodulin for fleshy fruit development. This study analyzed the expression of a family of six calmodulin genes (SlCaMs) during tomato fruit enlargement and ripening. All calmodulins showed a double peak expression pattern. The first flat peak appeared at 10-30 days after anthesis. Then their expression levels were declined to the basal level at mature green and breaker stages. Shortly after, a sharp and even higher peak appeared at turning stage. After red stage, the expression levels went down to a basal level. Among six calmodulins, SlCaM1 had the highest expression during fruit enlargement, whereas SlCaM2 was the major calmodulin during fruit ripening. Interestingly, SlCaMs showed different patterns in three ripening mutants rin, Nor and Nr. In particular, at the mature green and breaker, the expression levels of SlCaMs in those mutants were significantly higher than wild type. Furthermore, SlCaMs were upregulated by ethylene and the most dramatic stimulatory effect was observed for SlCaM2. Transient expression of sense SlCaM2 in mature green fruit delayed fruit ripening as compared to vector only control. In contrast, the introduction of anti-sense SlCaM2 resulted in faster fruit ripening. These results suggest that calmodulin is required for both fruit size and fruit maturation. Suppression of calmodulin gene expression at mature green and breaker fruit might be critical for fruit to initiate the ripening process.