Differential expression of calcium/calmodulin‐regulated SlSRs in response to abiotic and biotic stresses in tomato fruit

Abstract

Calcium has been shown to enhance stress tolerance, maintain firmness and reduce decay in fruits. Previously we reported that seven tomato SlSRs encode calcium/calmodulin-regulated proteins, and that their expressions are developmentally regulated during fruit development and ripening, and are also responsive to ethylene. To study their expressions in response to stresses encountered during postharvest handling, tomato fruit at the mature-green stage was subjected to chilling and wounding injuries, infected with Botrytis cinerea and treated with salicylic acid or methyl jasmonate. Gene expression studies revealed that the seven SlSRs differentially respond to different stress signals. SlSR2 was the only gene upregulated by all the treatments. SlSR4 acted as a late pathogen-induced gene; it was upregulated by salicylic acid and methyl jasmonate, but downregulated by cold treatment. SlSR3L was cold- and wound-responsive and was also induced by salicylic acid. SlSR1 and SlSR1L were repressed by cold, wounding and pathogen infection, but were upregulated by salicylic acid and methyl jasmonate. Overall, results of these expression studies indicate that individual SlSRs have distinct roles in responses to the specific stress signals, and SlSRs may act as a coordinator(s) connecting calcium-mediated signaling with other stress signal transduction pathways during fruit ripening and storage.

Tomato SR/CAMTA transcription factors SlSR1 and SlSR3L negatively regulate disease resistance response and SlSR1L positively modulates drought stress tolerance

“…In response to infection of B. cinerea , all the SlSRs showed upregulated expression patterns in leaf tissues, especially for SlSR1 , SlSR1L , SlSR3L and SlSR4 , whose expression levels were significantly upregulated (Figure 1). The B. cinerea -induced expression patterns of SlSRs in leaf tissues are somewhat different from the previous observation that the expressions of SlSR1 , SlSR1L , SlSR2L and SlSR3 in wounded tomato fruit were suppressed by B. cinerea [30], probably due to the tissue-specific expression feature of the SlSRs [29]. In contrast to the B. cinerea -induced expression patterns of SlSRs , expression of SlSR1 , SlSR1L , SlSR3 and SlSR3L in leaf tissues was upregulated in response to infection of Pst DC3000 (Figure 2).…”

“…The Pst DC3000-induced expression of SlSR1 is similar to that of the Arabidopsis AtSR1 , closely related to SlSR1 [29], whose expression was induced by Pst DC3000 [21]. However, infection of Pst DC3000 did not affect the expression of SlSR2 and SlSR3 but suppressed the expression of SlSR4 in leaf tissues (Figure 2), which is contrast to the observation that the expression of SlSR4 in fruit tissues was induced by B. cinerea [30]. Therefore, it seems reasonable that the expression of SlSRs is precisely controlled by complex mechanisms in response to infection from different pathogens.…”

“…Previous studies have identified a total of seven SlSRs genes in tomato and found that expression of SlSRs was regulated in tomato fruit by developmental cues and by biotic and abiotic environmental stress signals [29,30]; however, the biological functions of SlSRs in tomato response to biotic and abiotic stress remain unclear. In the present study, data from our VIGS-based functional analyses demonstrate that both SlSR1 and SlSR3L act as negative regulators of defense response against B. cinerea and Pst DC3000 while SlSR1L functions as a positive regulator of drought stress tolerance in tomato.…”

“…Further detailed analysis revealed that the SlSR genes showed differential expression patterns in tomato fruit in response to low temperature, mechanical injury, infection of the necrotrophic fungal pathogen B. cinerea , and treatments with the signaling molecules SA and MeJA [30]. However, direct genetic evidence supporting the involvement of the tomato SlSRs in biotic and abiotic stress responses is still lacking.…”

Recent Advances in Calcium/Calmodulin-Mediated Signaling with an Emphasis on Plant-Microbe Interactions

“…Follow-up studies showed that CAMTAs belong to a conserved transcription factor family that exists in all the examined multicellular eukaryotes Bouche et al, 2002;Yang and Poovaiah, 2002a;Finkler et al, 2007). The expression of CAMTAs is developmentally regulated (Yang et al, 2012) and responds to different abiotic and biotic signals (Yang and Poovaiah, 2002a;Yang et al, 2013). Target cis-elements for this family are (A/C/G) CGCG(T/C/G) (Yang and Poovaiah 2002a) and (A/C) CGTGT Doherty et al, 2009;Du et al, 2009;Kim et al, 2009b;Galon et al, 2010b).…”