A multilevel analysis of fruit growth of two tomato cultivars in response to fruit temperature

Abstract

Fruit phenotype is a resultant of inherent genetic potential in interaction with impact of environment experienced during crop and fruit growth. The aim of this study was to analyze the genetic and physiological basis for the difference in fruit size between a small ('Brioso') and intermediate ('Cappricia') sized tomato cultivar exposed to different fruit temperatures. It was hypothesized that fruit heating enhances expression of cell cycle and expansion genes, rates of carbon import, cell division and expansion, and shortens growth duration, whereas increase in cell number intensifies competition for assimilates among cells. Unlike previous studies in which whole-plant and fruit responses cannot be separated, we investigated the temperature response by varying fruit temperature using climate-controlled cuvettes, while keeping plant temperature the same. Fruit phenotype was assessed at different levels of aggregation (whole fruit, cell and gene) between anthesis and breaker stage. We showed that: (1) final fruit fresh weight was larger in 'Cappricia' owing to more and larger pericarp cells, (2) heated fruits were smaller because their mesocarp cells were smaller than those of control fruits and (3) no significant differences in pericarp carbohydrate concentration were detected between heated and control fruits nor between cultivars at breaker stage. At the gene level, expression of cell division promoters (CDKB2, CycA1 and E2Fe-like) was higher while that of the inhibitory fw2.2 was lower in 'Cappricia'. Fruit heating increased expression of fw2.2 and three cell division promoters (CDKB1, CDKB2 and CycA1). Expression of cell expansion genes did not corroborate cell size observations.

Fruit illumination stimulates cell division but has no detectable effect on fruit size in tomato (Solanum lycopersicum)

“…Histological, carbohydrate and gene expression analyses were conducted using pericarp tissue. Samples for histological analysis were harvested at breaker stage and fixed in a solution containing ethanol (96%), acetic acid, formaldehyde (37%) and Milli‐Q water, and later embedded following the Technovit protocol (Kulzer, Wehreim, Germany) as described in the studies carried out by Fanwoua et al () and Okello et al (). Slides (3 µm thick) were prepared, stained using 1% toluidine blue dye.…”

“…Images were observed using a microscope and nis‐elements software (Nikon Instruments, New York NY), and were analyzed using Image J software (National Institutes of Health, Rockville, MD). Pericarp thickness, the number of cell layers, longitudinal cell diameter, mean cell volume, tissue volume, tissue cell number and weighted pericarp cell volume were determined as described by Fanwoua et al () and Okello et al ().…”

“…Carbohydrate analysis was conducted using samples from fruits harvested at breaker stage. Sucrose, fructose, glucose and starch concentrations were determined using high‐performance anion‐exchange chromatography (HPAEC) as described in Okello et al (). Gene expression analysis was conducted with samples harvested at 6, 12, 18 and 35 DAA in experiment II.…”

“…Three biological replicates per treatment and harvest stage were obtained by pooling pericarp tissue from two of the six replicate plants. Total RNA extraction, DNase treatment, RNA qualitative and quantitative measurements and real‐time quantitative polymerase chain reaction (PCR) were conducted with primer pairs as described by Okello et al (). A total of 20 genes involved in either cell division or cell expansion regulation were studied.…”

Flexible and Shape‐Morphing Plant Sensors Designed for Microenvironment Temperature Monitoring of Irregular Surfaces

“…[ 5–8 ] Besides, fruit temperature is of significant importance in fruit planting and the process of storage and transportation. [ 9–13 ] The state‐of‐the‐art technologies for temperature monitoring in precision agriculture include using thermal imaging and rigid sensors fixed on leaves with fixtures, [ 12,14–17 ] which are low in spatial or temporal resolutions or fail to catch real‐time response of plant physiology.…”