Should Starch Metabolism Be a Key Point of the Climacteric vs. Non-climacteric Fruit Definition?
Résumé
The usual definition of the difference between climacteric and non-climacteric fruit relies on the fact that climacteric fruit ripens with concomitant increases of respiration and ethylene production, whereas barely any change in these two metabolisms occurs in non-climacteric fruit (Cherian et al., 2014). These authors list a series of climacteric fruit, such as tomato, banana, apple and mango, and a series of non-climacteric fruit such as strawberry, melon and grape. I think melon is a particular case, with climacteric and non-climacteric cultivars (Obando-Ulloa et al., 2009; Saladié et al., 2015), and this will not be detailed here. Other fruits have such climacteric and non-climacteric cultivars within a same species, for example Asian pears (Itai and Fujita, 2008) and plums (Minas et al., 2015). There have been many other reviews and articles over the last decade, regarding the differences between climacteric and non-climacteric fruit classes (Paul et al., 2012; Osorio et al., 2013; Saladié et al., 2015; Farcuh et al., 2017; Fuentes et al., 2019), but none pointed out that starch accumulation or breakdown could be a cornerstone in the definition of these two fruit classes. A quick data review, as detailed below, shows that most climacteric fruit accumulate starch before the onset of ripening, then starch is broken down to soluble sugars after the inception of ripening, whereas in the non-climacteric fruit the starch content drops very rapidly after anthesis, and they accumulate mainly soluble sugars throughout development and ripening. This big difference leads to different harvest strategies: climacteric fruit can be picked early, and the starch reserve will be converted to sugars over postharvest stages, whereas the non-climacteric fruit should be picked when the desired soluble sugar level is reached. However, starch metabolism is rarely mentioned as a key difference between climacteric and non-climacteric fruit. Osorio et al. (2012) suggested that the regulation of starch synthesis may be part of this difference, when comparing climacteric (tomato) and non-climacteric (pepper) fruit transcripts around the onset of ripening. Thus, I will first list starch contents in some climacteric and non-climacteric fruit, then I will review rapidly the starch synthesis and the starch breakdown metabolisms in plants, and finally I will discuss research perspectives.
Domaines
Biologie végétale
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