Ripening-Regulated Susceptibility of Tomato Fruit toBotrytis cinereaRequiresNORBut NotRINor Ethylene    

Abstract

Fruit ripening is a developmental process that is associated with increased susceptibility to the necrotrophic pathogen Botrytis cinerea. Histochemical observations demonstrate that unripe tomato (Solanum lycopersicum) fruit activate pathogen defense responses, but these responses are attenuated in ripe fruit infected by B. cinerea. Tomato fruit ripening is regulated independently and cooperatively by ethylene and transcription factors, including NON-RIPENING (NOR) and RIPENING-INHIBITOR (RIN). Mutations in NOR or RIN or interference with ethylene perception prevent fruit from ripening and, thereby, would be expected to influence susceptibility. We show, however, that the susceptibility of ripe fruit is dependent on NOR but not on RIN and only partially on ethylene perception, leading to the conclusion that not all of the pathways and events that constitute ripening render fruit susceptible. Additionally, on unripe fruit, B. cinerea induces the expression of genes also expressed as uninfected fruit ripen. Among the ripening-associated genes induced by B. cinerea are LePG (for polygalacturonase) and LeExp1 (for expansin), which encode cell wall-modifying proteins and have been shown to facilitate susceptibility. LePG and LeExp1 are induced only in susceptible rin fruit and not in resistant nor fruit. Thus, to infect fruit, B. cinerea relies on some of the processes and events that occur during ripening, and the fungus induces these pathways in unripe fruit, suggesting that the pathogen itself can initiate the induction of susceptibility by exploiting endogenous developmental programs. These results demonstrate the developmental plasticity of plant responses to the fungus and indicate how known regulators of fruit ripening participate in regulating ripening-associated pathogen susceptibility.

Transcriptome and Metabolite Profiling Show That APETALA2a Is a Major Regulator of Tomato Fruit Ripening

“…The expression of AP2a appeared to be reduced in all four mutants. Our results suggest that, although AP2a appears at first sight to be a negative regulator of ripening through inhibition of ethylene production, it is itself positively regulated by essential regulators of ripening, like CNR, RIN, and NOR (Barry et al, 2005;Giovannoni, 2007;Cantu et al, 2009), and its expression is ethylene dependent, as shown by its downregulation in the Gr mutant. Next, to test whether the CNR protein could bind directly to the AP2a promoter, we expressed the full-length CNR protein tagged with glutathione S-transferase (GST) (GST-CNR) in Escherichia coli ( Figure 5B.…”

Phenotypic and molecular characterization of a tomato (Solanum lycopersicum L.) F2 population segregation for improving shelf life

“…The rin (0.04 mg/100 g) and nor (0.15 mg/100 g) mutants recorded low lycopene content, but alc (0.73 mg/100 g) displayed a significantly higher level similar to those of Indian cultivars, and Kopeliovitch et al (1980) have reported a lycopene content in alc of 1.182 mg/100 g. The low lycopene contents of the nor and rin ripening mutants agree with the results of others Tigchelaar et al, 1976). In both nor and rin mutants, the fruits develop normally before the mature green stage, but once mature, they fail to synthesize lycopene and other carotenoids (Cantu et al, 2009). However, the F 1 (alc x 'Pusaruby') showed significantly higher values (1.75 mg/100 g), whereas the values for other hybrids were similar to those of the Indian cultivars.…”

Different ROS-Scavenging Properties of Flavonoids Determine Their Abilities to Extend Shelf Life of Tomato

“…Shelf life of tomato is determined by two processes: the rate of fruit softening during overripening (which is the stage that follows commercial maturity, when the fruit softens and loses its organoleptic properties, including its characteristic taste and flavor), and susceptibility to opportunistic pathogens such as Botrytis cinerea (Cantu et al, 2009). B. cinerea, better known as gray mold, is the second most important fungal pathogen of plants, economically (Dean et al, 2012).…”