Abscisic acid perception and signaling transduction in strawberry: A model for non-climacteric fruit ripening

Abstract

On basis of fruit differential respiration and ethylene effects, climacteric and non-climacteric fruits have been classically defined. Over the past decades, the molecular mechanisms of climacteric fruit ripening were abundantly described and found to focus on ethylene perception and signaling transduction. In contrast, until our most recent breakthroughs, much progress has been made toward understanding the signaling perception and transduction mechanisms for abscisic acid (ABA) in strawberry, a model for non-climacteric fruit ripening. Our reports not only have provided several lines of strong evidences for ABA-regulated ripening of strawberry fruit, but also have demonstrated that homology proteins of Arabidopsis ABA receptors, including PYR/PYL/RCAR and ABAR/CHLH, act as positive regulators of ripening in response to ABA. These receptors also trigger a set of ABA downstream signaling components, and determine significant changes in the expression levels of both sugar and pigment metabolismrelated genes that are closely associated with ripening. Soluble sugars, especially sucrose, may act as a signal molecular to trigger ABA accumulation through an enzymatic action of 9-cis-epoxycarotenoid dioxygenase 1 (FaNCED1). This minireview offers an overview of these processes and also outlines the possible, molecular mechanisms for ABA in the regulation of strawberry fruit ripening through the ABA receptors. Abscisic acid perception and signaling transduction in strawberryA model for non-climacteric fruit ripening Our recent reports have provided strong evidences that ABA plays a crucial role in the regulation of ripening related-gene expression through ABA perception and signaling transduction in strawberry fruit.9,10 These and previous studies provide several lines of evidences that the interaction between sugar and ABA may be a core mechanism in regulation of the ripening of nonclimacteric fruits. ABA is Required for Strawberry Fruit RipeningAs a plant hormone, ABA not only plays a central role in the adaptation of plants to adverse conditions, but also regulates various aspects of plant growth and development, such as seed dormancy, seedling growth and fruit development.11-13 Notably, ABA is considered to play even more important roles than that of ethylene in fruit maturation and senescence.14 Ripening of strawberry (Fragaria x ananassa), a model for non-climacteric fruits, is previously reported to be promoted by ABA. 15 In accordance with this notion, our recent reports also showed that exogenous ABA can significantly accelerate strawberry fruit ripening, and a remarkable decrease in ABA content that results from the downregulation of the transcripts of a 9-cis-epoxycarotenoid dioxygenase gene (FaNCED1) by virus-induced gene silencing (VIGS), can significantly retard the ripening process.9 To our knowledge, this is the first direct molecular evidence on the requirement of ABA for strawberry fruit ripening.

Type 2C protein phosphatase ABI1 is a negative regulator of strawberry fruit ripening

“…In recent years, not only has ABA been shown to play important roles in perception and signal transduction involved in the regulation of Arabidopsis seed germination, seedling growth, and stomatal movement (Fujii et al ., 2009; Ma et al ., 2009; Melcher et al ., 2009; Miyazono et al ., 2009; Nishimura et al ., 2009; Santiago et al ., 2009; Shang et al ., 2010), but much progress has also been made toward a better understanding of the molecular mechanisms that underlie the roles of ABA in the regulation of fleshy fruit ripening (Chai et al ., 2011; Jia et al ., 2011; Li et al ., 2011; Sun et al ., 2011, 2012). Nevertheless, many ABA signalling components involved in fruit ripening remain to be elucidated.…”

“…The down-regulation of the expression of ABA receptor genes Mg-chelatase H subunit ( FaABAR/CHLH ) or pyrabactin resistance 1 gene ( FaPYR1 ) can destroy strawberry fruit red colouring, indicating that both FaABAR/CHLH and FaPYR1 proteins are positive regulators of fruit ripening (Chai et al ., 2011; Jia et al ., 2011; Li et al ., 2011). A significant reduction in SINCED1 activity leads to a decline in the transcription of genes encoding major cell wall catabolic enzymes, indicating that ABA affects cell wall catabolism during tomato fruit ripening (Sun et al ., 2012).…”

A roadmap for research in octoploid strawberry

“…Unlike what is found in climacteric fruits, experiments with F. × ananassa have shown that ABA is clearly a promoter of ripening in strawberry 108 . VIGS of FaNCED1, encoding a key enzyme in ABA biosynthesis, produced white fruits, and this phenotype was rescued by exogenous ABA 109 .…”

<i>n</i>-Propyl dihydrojasmonates influence ethylene signal transduction in infected apple fruit by <i>Botrytis cinerea</i>

“…ABA can regulate abiotic and biotic stresses in fruit and can also regulate maturation processes in nonclimacteric fruit such as grapes, strawberries (Fragaria × ananassa) and cherries (Prunus avium) (Li et al, 2011;Wheeler et al, 2009;Falchi et al, 2014). ABA treatment increased the pathogen resistance of fruit (Sivakumaran et al, 2016;Lievens et al, 2017).…”