Abstract
BackgroundFruit ripening is a complicated development process affected by a variety of external and internal cues. It is well established that calcium treatment delays fruit ripening and senescence. However, the underlying molecular mechanisms remain unclear.ResultsPrevious studies have shown that calcium/calmodulin-regulated SR/CAMTAs are important for modulation of disease resistance, cold sensitivity and wounding response in vegetative tissues. To study the possible roles of this gene family in fruit development and ripening, we cloned seven SR/CAMTAs, designated as SlSRs, from tomato, a model fruit-bearing crop. All seven genes encode polypeptides with a conserved DNA-binding domain and a calmodulin-binding site. Calmodulin specifically binds to the putative targeting site in a calcium-dependent manner. 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. By contrast, only minor alterations were noted for ripening mutant nor and Nr fruit. In addition, ethylene treatment of mature green wildtype fruit transiently stimulated expression of all SlSRs within one to two hours.ConclusionsThis study indicates that SlSR expression is influenced by both the Rin-mediated developmental network and ethylene signaling. The results suggest that calcium signaling is involved in the regulation of fruit development and ripening through calcium/calmodulin/SlSR interactions.
Highlights
Fruit ripening is a complicated development process affected by a variety of external and internal cues
Seven SR/CAMTAs are expressed in tomato There are six SR/CAMTAs (AtSR1-6) in the Arabidopsis genome and all of them are expressed in tissues [26]
The primer sets for cloning three of them, SlSR1, SlSR2 and SlSR3, were designed directly from the available Unigenes/ESTs based on the amino acid sequence alignment with Arabidopsis AtSRs in the N-terminal and C-terminal regions
Summary
Fruit ripening is a complicated development process affected by a variety of external and internal cues. It is well established that calcium treatment delays fruit ripening and senescence. Fruit quality and postharvest shelf life are dependent upon the control of ripening. Fruits are grouped into two ripening types, climacteric and non-climacteric. The ripening of non-climacteric fruits, such as strawberry and grape is mediated by an ethylene-independent process with little changes in respiration rate (reviewed in [1,2,3]). The fruit ripening process for both fruit types is affected by environmental cues such as temperature change, wounding and pathogen infection. Calcium has been shown to be important in controlling fruit ripening and quality by delaying ripening and maintaining firmness. The molecular mechanisms whereby calcium retards fruit ripening remain elusive
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
