Ethylene-abscisic acid interaction and its influence on the volatile compounds production during Micro-Tom Tomato (Solanum lycopersicum) fruit ripening

Abstract

Ripening is a complex process from which fruits develop their sensorial characteristics, such as changes in texture, color, accumulation of soluble sugars, decreasing in organic acids content, and changes in flavor, an attribute formed by the taste and aroma, crucial to the quality of the fruit. In tomatoes (Solanum lycopersicum), 20-30 volatile metabolites contribute significantly to the aroma, the majority being originated from the degradation pathways of fatty acids, amino acids and terpenes. Regarding the regulation of these pathways, the role of plant hormones on the biosynthesis of volatile compounds has been investigated. Although there is extensive literature including the role of ethylene on ripening and induction of transcription of genes encoding enzymes associated with the formation of esters, alcohols, aldehydes, terpenes and other volatile matter in climacteric fruits, the knowledge about the involvement of other hormones, such as indole-3-acetic acid (IAA), methyl jasmonate (MJ), and abscisic acid (ABA) in the biosynthetic pathways of volatile compounds is scarce. Taking these observations as a basis, the aim of this study is to assess the extent of the influence of abscisic acid on the formation of volatile compounds in Micro-Tom tomato fruit. To this, fruit will be harvested at the mature green stage and will be injected with ABA and ripening parameters, such as ethylene production, respiration and color, which will be monitored and compared with fruits of the control group. Fruit treated with ethylene action inhibitor, 1-methylcyclopropene (1-MCP) in combination with ABA will be used to assess whether the effects of ABA are ethylene-dependent. An ABA synthesis inhibitor, fluridone, will be used to assess the formation of aroma in fruit ripening with reduced levels of ABA. The volatiles will analyzed by gas chromatography-mass spectrometry (GC-MS). The transcription pattern of genes related to aroma biosynthesis (SlLOXC, SlHPL, SlADH2, SlCCD1A and SlCCD1B) will be also evaluated in all experimental groups. The results will contribute to the comprehension of the ABA role on the formation of aroma during tomato fruit ripening and also its relationship with the ethylene on the regulation of this process.