Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2012
Publication Date: 2/13/2012
Citation: Yang, T., Peng, H., Whitaker, B.D., Conway, W.S. 2012. Characterization of a calcium/calmodulin-regulated SR/CAMTA gene family during tomato fruit development and ripening. Biomed Central (BMC) Plant Biology. 12:19.
Interpretive Summary: Nearly a quarter of all fresh fruits and vegetables in the U.S. market are lost after harvest due to the damages caused by wounding, low temperature and pathogens, as well as fruit softening caused by gaseous ethylene. The relationship of calcium to postharvest maladies is well known. However, the underlying molecular mechanisms remain unclear. Previous studies indicated that a specific calcium-regulated gene family in Arabidopsis plays an important role in disease resistance, cold sensitivity and wounding response. To better understand gene family’s role in fruit ripening, we cloned seven of these genes from tomato, one of the most important horticultural crops. All those genes were highly and yet differently expressed during fruit development and ripening. Their expression patterns were also changed in a particular tomato with a ripening mutation, and were all affected by ethylene. This research will help researchers and industry partners to understand the mechanisms of fruit ripening, so as to maintain tomato fruit quality and extend fruit shelf life.
Technical Abstract: It is well established that calcium treatment delays fruit ripening and senescence. However, the underlying molecular mechanisms remain unclear. Previous studies have shown that calcium/calmodulin-regulated SR/CAMTA genes are important for modulation of disease resistance, cold sensitivity and wounding response in vegetative tissues. To study possible roles of this gene family in fruit development and ripening, we cloned seven SR/CAMTAs, from tomato. All seven genes encode polypeptides with a conserved DNA-binding domain and a calmodulin-binding site. Calmodulin specifically binds to the putative calmodulin-binding site. All SlSRs were highly yet differentially expressed during fruit development and ripening. Most notably, the expression of SlSR2 was scarcely detected at the mature green and breaker stages, two critical stages of fruit development and ripening; and SlSR3L and SlSR4 were expressed exclusively in fruit tissues. During the developmental span from 10 to 50 days post anthesis, the expression profiles of all seven SlSRs were dramatically altered in ripening mutant rin compared with wildtype fruit. In addition, ethylene treatment of mature green wildtype fruit transiently stimulated expression of all SlSRs. Thus, SlSR expression is influenced by both the Rin-mediated developmental network and ethylene signaling. Our results suggest that calcium signaling is involved in the regulation of fruit development and ripening through calcium/calmodulin/SlSR interactions.