Exogenous cytokinin application to Actinidia chinensis var. deliciosa ‘Hayward’ fruit promotes fruit expansion through water uptake

Abstract

Exogenous application of a cytokinin-like compound forchlorfenuron (CPPU) can promote fruit growth, although often at the expense of dry matter (DM), an important indicator of fruit quality. Actinidia chinensis var. deliciosa ‘Hayward’ fruit are very responsive to CPPU treatments, but the mechanism underlying the significant fruit weight increase and associated decrease in DM is unclear. In this study, we hypothesised that CPPU-enhanced growth increases fruit carbohydrate demand, but limited carbohydrate supply resulted in decreased fruit DM. During fruit development, CPPU effects on physical parameters, metabolites, osmotic pressure and transcriptional changes were assessed under conditions of both standard and a high carbohydrate supply. We showed that CPPU increased fruit fresh weight but the dramatic DM decrease was not carbohydrate limited. Enhanced glucose and fructose concentrations contributed to an increase in soluble carbohydrate osmotic pressure, which was correlated with increased water accumulation in CPPU-treated fruit and up-regulation of water channel aquaporin gene PIP2.4 at 49 days after anthesis. Transcipt analysis suggested that the molecular mechanism contributing to increased glucose and fructose concentrations was altered by carbohydrate supply. At standard carbohydrate supply, the early glucose increase in CPPU fruit was associated with reduced starch synthesis and increased starch degradation. When carbohydrate supply was high, the early glucose increase in CPPU fruit was associated with a general decrease in starch synthesis but up-regulation of vacuolar invertase and fructokinase genes. We conclude that CPPU affected fruit expansion by increasing the osmotically-driven water uptake and its effect was not carbohydrate supply-limited.

Carbon starvation reduces carbohydrate and anthocyanin accumulation in red‐fleshed fruit via trehalose 6‐phosphate and MYB27

“…In another study, exogenous cytokinin application to ‘Hayward’ kiwifruit reduced starch accumulation early in fruit development, and this was associated, similarly to this current study, with a down‐regulation of another ADP‐GLUCOSE PYROPHOSPHORYLASE LARGE SUBUNIT , APL2 (Nardozza et al ). BAM9 , a β‐amylase gene coding for a catalytically inactive enzyme, was previously associated with starch degradation and turnover early in fruit development (Nardozza et al ; Nardozza et al ). Under carbon starvation, BAM9 was up‐regulated from 12 WAMB, suggesting a role in releasing fruit‐stored carbohydrate to support fruit development when imported sugars were limited.…”

Evolution and roles of cytokinin genes in angiosperms 1: Do ancient IPTs play housekeeping while non-ancient IPTs play regulatory roles?

“…Cytokinins (CKs) are a class of plant hormones that play essential roles in many aspects of plant development, including the delay of leaf senescence 1 , root proliferation 2,3 , apical dominance 4 , shoot meristem function [5][6][7] , regulation of reproductive meristem activity 8 , fruit development 9 , and nutritional signaling 10,11 . In addition, CKs play important and complex roles in environmental stress responses 12,13 .…”

Efecto del anillado de ramas, thidiazuron y ácido giberélico en el tamaño del fruto de palto “Hass” (Persea americana Mill.)

“…Resultados positivos en el calibre de los frutos encontraron Ish-Am et al (2007) en frutos de palto 'Ettinger' con otra citoquinina sintética, la Benziladenina, a concentraciones menores a 100 ppm. Es posible que estos 404 efectos tengan relación con el incremento del poder de sumidero de los frutos como parecen sugerir los resultados reportados por Nardozza et al (2017), quienes encontraron que las aplicaciones de la citoquinina sintética CPPU aumentaron el peso de los frutos de kiwi por incremento de la demanda de carbohidratos y al haber limitación en su abastecimiento, absorben más agua. También es posible que la citoquinina participe como agente de activación en la intensificación de las divisiones celulares, asociadas con los estados iniciales del crecimiento del fruto (Taiz y Zeiger, 2006) Ensayo 3: Efecto de la aplicación de ácido giberélico (AG 3 ) De forma general, a un nivel de significación estadística de P=0,05, los diámetros y longitudes de los frutos no mejoraron con los tratamientos y fueron iguales a los registrados para los árboles testigo, según se observa en la Tabla 3.…”