Calcium- and hormone-driven regulation of secondary metabolism and cell wall enzymes in grape berry cells

Abstract

The efficacy of calcium sprays for improving fleshy fruit resistance to abiotic/biotic stress and enhancement of fruit shelf life has increasingly been explored. However, because calcium is a powerful secondary messenger in many signaling pathways, including those driven by abscisic acid (ABA) and jasmonates, it may interfere with the biosynthesis of specialized metabolites highly important for fruit and wine quality, such as phenolic compounds. In this study, a combination of biochemical and molecular biology approaches were applied to grape cell cultures and detached grape berries, in order to investigate the effect of calcium in the modulation of enzymes involved in the biosynthesis of phenolic compounds and in cell wall organization. Concentrations up to 10 mM CaCl did not affect cell growth, size or viability, but triggered modifications in total phenolics content, particularly in anthocyanin levels in grape cell suspensions. The effects of calcium applied alone or in combination with ABA or methyl jasmonate (MeJA) were visible in several branches of specialized metabolic pathways, confirming that the calcium-hormone interplay regulates the expression of phenylalanine ammonia lyase (PAL), stilbene synthase (STS), dihydroflavonol reductase (DFR) and UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT). The activity of PAL and UFGT enzymes was also specifically modulated by calcium, ABA and MeJA. These results closely correlated to the modifications observed in the expression of VvAM1 and VvABCC1 encoding vacuolar anthocyanin transporters. Modulation of the expression and activity of pectin methyl esterases (PME) and polygalacturonases (PG) by calcium was also evident, confirming an important role of calcium in cell wall organization via the regulation of enzyme activity, besides its well-known role in the formation of cross links between pectin molecules. Overall, this study uncovers important biochemical mechanisms induced by calcium and stress hormones on grape berries, and highlights the need to consider the consequences of calcium treatments and stress for fruit quality.

Recent Advances in Hormonal Regulation and Cross-Talk during Non-Climacteric Fruit Development and Ripening

“…However, its molecular implication on phytohormone crosstalk regulation is still not very clear. Studies of ABA and MeJA applied alone or in combination with calcium to grape suggested a calcium-hormone interplay that regulated the expression and activity of flavonoid biosynthetic enzymes [221]. , and jasmonic acid isoleucine conjugate (JA-Ile).…”

Effects of calcium chloride treatment on softening in red raspberry fruit during low‐temperature storage

“…The carboxylic groups of de‐esterified pectins are cross‐linked by Ca 2+ in middle lamella of cell wall, which helps to strengthen the cell‐wall structure (Demarty, Morvan, & Thellier, 1984; Thor, 2019). To date, several studies have conducted to study the effects of postharvest calcium treatment on storage quality, softening and cell wall degradation during fruit ripening (Belge, Goulao, Comabella, Graell, & Lara, 2017; Gao, Xiong, Li, Chen, & Zhu, 2019; Liu et al., 2017; Martins, Garcia, Costa, Sottomayor, & Gerós, 2018). However, the influence of calcium on softening of red raspberry fruit stored at low temperature has not been explored.…”

Prohexadione-calcium on downy mildew and botrytis bunch rot epidemiology, and yield and technological and phenolic parameters of the Merlot vine cultivar in the highland region of southern Brazil

“…The right balance between productivity and fruit quality is a particularly challenging aspiration in viticulture (MARTINS et al, 2018). Currently, the right parameters used for the harvest decision are the sanity and chemical quality of the grape.…”