Calmodulin Gene Expression in Response to Mechanical Wounding and Botrytis cinerea Infection in Tomato Fruit.

Hui Peng,Tianbao Yang,Wayne M Jurick Ii

doi:10.3390/plants3030427

Abstract

Calmodulin, a ubiquitous calcium sensor, plays an important role in decoding stress-triggered intracellular calcium changes and regulates the functions of numerous target proteins involved in various plant physiological responses. To determine the functions of calmodulin in fleshy fruit, expression studies were performed on a family of six calmodulin genes (SlCaMs) in mature-green stage tomato fruit in response to mechanical injury and Botrytis cinerea infection. Both wounding and pathogen inoculation triggered expression of all those genes, with SlCaM2 being the most responsive one to both treatments. Furthermore, all calmodulin genes were upregulated by salicylic acid and methyl jasmonate, two signaling molecules involved in plant immunity. In addition to SlCaM2, SlCaM1 was highly responsive to salicylic acid and methyl jasmonate. However, SlCaM2 exhibited a more rapid and stronger response than SlCaM1. Overexpression of SlCaM2 in tomato fruit enhanced resistance to Botrytis-induced decay, whereas reducing its expression resulted in increased lesion development. These results indicate that calmodulin is a positive regulator of plant defense in fruit by activating defense pathways including salicylate- and jasmonate-signaling pathways, and SlCaM2 is the major calmodulin gene responsible for this event.

Highlights

Calcium is a universal second messenger involved in growth, development and mediating responses to a variety of abiotic and biotic stresses in plants [1,2,3]
To study the effect of wounding on SlCaMs expression, mature green stage fruit were selected because this is the specific stage that is routinely harvested by the tomato industry, Without wounding, the most abundantly expressed genes were SlCaM1 and SlCaM5 (Figure 1)
We found that six SlCaMs, especially SlCaM2, in tomato fruits were upregulated by mechanical wounding, necrotrophic fungal infection, Salicylic acid (SA) and Jasmonic acid (JA)

Summary

Introduction

Calcium is a universal second messenger involved in growth, development and mediating responses to a variety of abiotic and biotic stresses in plants [1,2,3]. Calmodulin (CaM) is a ubiquitous calcium sensor in plants, and plays an important role in almost all aspects of cell activity [4,5,6]. In contrast to animals which have one or a few CaM genes encoding identical isoforms, plants have multiple genes encoding more diversified isoforms. CaM genes, even genes encoding the same isoform, are differentially expressed in response to numerous external stimuli such as touch, heat shock, cold, light, pathogens, and to phytohormones. In Arabidopsis, seven CaM genes encode four highly conserved isoforms. A loss-of-function mutant in Arabidopsis AtCaM2 affects pollen germination [7]. Specific CaM isoforms SCaM-4 and SCaM-5, are highly induced either by a fungal elicitor or pathogen attack, whereas three other

Results

Discussion

Conclusion