Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2014
Publication Date: 8/29/2014
Citation: Peng, H., Yang, T., Jurick II, W.M. 2014. Calmodulin gene expression in response to mechanical wounding and Botrytis cinerea infection in tomato fruit. PLANTS. 3:427-441.
Interpretive Summary: Tomato is the second most important vegetable crop worldwide. However, nearly 25% of the tomatoes are lost after harvest due to wounding and decay. Pre- and post- harvest application of calcium has been shown to reduce decay, delay ripening and maintain firmness in fruits. Yet, the underlying molecular mechanisms involved in these beneficial effects remain unclear. Previous studies have shown that calmodulins, the calcium sensor genes that control calcium related action, are important for modulation of disease resistance in tomatoes. The studies reported in this article further examined the effect of postharvest handling conditions and chemical treatments on the changes in calmodulins and the improvement in plant disease resistance of tomatoes. These results provide new knowledge that can be used by plant breeders or growers to improve fruit postharvest quality and reduce decay.
Technical Abstract: Calmodulin, a ubiquitous calcium sensor, plays an important role in decoding the stress-triggered intracellular calcium changes and regulates the functions of numerous target proteins involved in various physiological responses in plants. To determine the functional significance of calmodulin in fleshy fruit, expression studies of six calmodulin genes in the mature-green stage tomato fruit were carried out in response to mechanical injury and Botrytis cinerea attack. Both wounding and pathogen inoculation triggered expression of all six calmodulins. Of them, SlCaM2 was the most responsive gene to both treatments. Furthermore, all calmoduline genes were upregulated by salicylic acid and methyl jasmonate, two signal molecules involved in plant defense. In addition to SlCaM2, SlCaM1 was highly responsive to those two compounds. However, SlCaM2 exhibited a faster and more profound response than SlCaM1. Overexpression of SlCaM2 in fruit enhanced the resistance to Botrytis-induced decay, whereas reducing its expression resulted in a faster decay. These results indicate that calmodulin is a positive regulator of plant defense in fruit by activating defense pathways including salicylate- and jasmonate- signalings, and SlCaM2 is the major calmodulin gene responsible for this event.