Molecular Characterization of a Strawberry FaASR Gene in Relation to Fruit Ripening

BACKGROUND: ABA-, stress- and ripening-induced (ASR) proteins have been reported to act as a downstream component involved in ABA signal transduction. Although much attention has been paid to the roles of ASR in plant development and stress responses, the mechanisms by which ABA regulate fruit ripening at the molecular level are not fully understood. In the present work, a strawberry ASR gene was isolated and characterized (FaASR), and a polyclonal antibody against FaASR protein was prepared. Furthermore, the effects of ABA, applied to two different developmental stages of strawberry, on fruit ripening and the expression of FaASR at transcriptional and translational levels were investigated. METHODOLOGY/PRINCIPAL FINDINGS: FaASR, localized in the cytoplasm and nucleus, contained 193 amino acids and shared common features with other plant ASRs. It also functioned as a transcriptional activator in yeast with trans-activation activity in the N-terminus. During strawberry fruit development, endogenous ABA content, levels of FaASR mRNA and protein increased significantly at the initiation of ripening at a white (W) fruit developmental stage. More importantly, application of exogenous ABA to large green (LG) fruit and W fruit markedly increased endogenous ABA content, accelerated fruit ripening, and greatly enhanced the expression of FaASR transcripts and the accumulation of FaASR protein simultaneously. CONCLUSIONS: These results indicate that FaASR may be involved in strawberry fruit ripening. The observed increase in endogenous ABA content, and enhanced FaASR expression at transcriptional and translational levels in response to ABA treatment might partially contribute to the acceleration of strawberry fruit ripening

Ethylene and carbon dioxide production by developing strawberries show a correlative pattern that is indicative of ripening climacteric fruit

Contains fulltext : 35876pub.pdf (publisher's version ) (Closed access)Laser photoacoustic spectroscopy continuously quantified the ethylene (C2H4) produced by strawberry flowers and fruits developing in planta. C2H4 was first detected as flower buds opened and exhibited diurnal oscillations (to approximately 200 pl flower(-1) h(-1)) before petal abscission. Exogenous application of silver thiosulphate (STS) to detached flowers inhibited petal abscission and flower senescence. In fruit, C2H4 production was maintained at a 'low level' (10-60 pl fruit(-1) h(-1)) until fruit expanded when levels increased in a diurnal pattern (to 200 pl fruit(-1) h(-1)). After expansion, C2H4 production declined to a low level until fruit attained the red-ripe stage for at least 24 h. After this time, C2H4 levels increased linearly (no diurnal fluctuation) to approximately 1 nL fruit(-1) h(-1). Twenty-four hours after the re-initiation of C2H4 production by red fruit, CO2 levels increased approximately three-fold, indicative of a respiratory climacteric. STS applied to fruits developing in planta and dissected fruit parts ex situ established that C2H4 production is regulated by negative feedback until fruits had expanded. The C2H4 produced by red-ripe fruit was regulated by positive feedback. Anti-1-amino-cyclopropane-1-carboxylic acid oxidase IgG localization identified immunoreactive antigens of 40 and 30 kDa (M-r) within the fruit achenes of expanding and red-ripe fruit. Analysis of dissected fruit showed that seed C2H4 accounts for 50% the C2H4 that is detectable from ripe fruit