Mountain papaya ( Vasconcellea pubescens ) is a climacteric fruit that develops a strong and characteristic aroma during ripening. Esters are the main volatile compounds produced by the fruit, and most of them are dependent on ethylene. As esters are synthesized through alcohol acyltransferases (AAT), a full-length cDNA (VpAAT1) was isolated that displayed the characteristic motifs of most plant acyltransferases. The full-length cDNA sequence was cloned and expressed in yeasts, obtaining a functional enzyme with high AAT activity toward the formation of benzyl acetate. The transcript accumulation pattern provided by qPCR analysis showed that the VpAAT1 gene is expressed exclusively in fruit tissues and that a high level of transcripts is accumulated during ripening. The increase in VpAAT1 transcripts in fruit is coincident with the increase in AAT activity; transcript accumulation is induced by ethylene, and it is avoided by 1-methylcyclopropene (1-MCP) treatment. The data indicate that VpAAT1 is involved in aroma formation and that ethylene plays a major role in regulating its expression.

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Rain-induced cherry fruit cracking is one of the most important problems in the cherry industry, and its occurrence causes significant economic losses. Sweet cherry (Prunus avium [L.] L.) is a non-climacteric fruit affected by both abscisic acid (ABA) and methyl jasmonate (MeJA) during development. The objective of this study was to evaluate the effect of these phytohormones on cracking susceptibility and quality parameters of sweet cherry fruit ('Bing'), located in the central region of Chile. During two seasons, independent pre-harvest applications of ABA (0.1 mM) and MeJA (0.4 mM) or both combined, at fruit developmental stages of fruit set or fruit color change, significantly reduced the number of mature cracked fruit after 6 h of immersion in water (p < 0.05). In both seasons the combinations of ABA and MeJA applied at fruit set reducing cracking index in an 87% compared to the control without compromising the weight or the diameter of the fruits. Moreover, in the second season ABA and MeJA applications at fruit set increased fruit firmness (11% and 6% respectively) and fruit color parameters regardless of the fruit stage at application, although slight decreases in soluble solids content were observed in most of the treatments.

Rain-induced cracking in fruits of sweet cherry (Prunus avium [L.]) is a problem in most producing areas of the world and causes significant economic losses. Different orchard management practices have been employed to reduce the severity of this problem, although a complete solution is not yet available. Fruit cracking is a complex phenomenon and there are many factors that seem to be involved in its development. During the last decade, genomic and biochemical approaches have provided new insights on the different mechanisms that could be involved in the differential susceptibility shown by commercial cultivars. For instance, sweet cherry genome and transcriptome sequencing information have provided new opportunities to study the expression and structure of genes involved in cracking, which may help in the development of new tolerant cultivars. The present review summarizes, discuss, and integrate most of the recently generated information in cultural practices, physiology, biochemistry, and genetics in relation to cracking in sweet cherries.

Rain-induced cracking before harvest is the major cause of crop loss in sweet cherry (Prunus avium [L.] L.) In order to better understand the relationship between cherry fruit cracking and gene expression, the transcriptional patterns of six genes related to cell wall modification and cuticular wax biosynthesis were analyzed during fruit setting (FS), fruit color change (FC) and fruit ripening (FR), employing two contrasting cultivars: the cracking resistant 'Kordia' and the cracking susceptible 'Bing'. The transcription levels of AP2/EREBP-type transcription factor (PaWINB), wax synthase (WS), β-ketoacyl-CoA synthase (PaKCS6), and β-galactosidase (β-Gal) showed higher levels in 'Kordia' than in 'Bing' during the FS stage, while similar values were observed in both cultivars at FR stage. In contrast to that pattern, transcription levels of expansin (PaEXP1) were higher at FR stage in 'Kordia' than in 'Bing'. Transcript profile of lipid transport protein gene (PaLTPG1) decreased during fruit development, with higher levels in 'Bing' than in 'Kordia' at FC and FR stages suggesting no relation with cracking tolerance. The expression profiles of PaWINB, WS, PaKCS6, and β-Gal suggest that they are genes involved in conferring cracking tolerance, likely due to their function in cuticle deposition during early stages of fruit development. In addition, a greater expression level of expansin gene would allow for a faster growth rate in 'Kordia' at FR stage.

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During the last few years, many studies have directed their efforts at elucidating the molecular mechanisms that regulate plant response to cold stress using gene expression analysis. Quantitative real-time qRT-PCR has great advantages compared to traditional transcriptional detection methods due to its high sensibility, reproducibility, and specificity for the detection of low quantities of RNA. However, this technique requires the use of one or several housekeeping genes. In this work, the expression stabilities of six housekeeping genes (EF1a, ACT, a-TUB, PDF, SAND, and UBC) during the cold acclimation of E. globulus plants was analyzed. An ELIP gene that responds to photooxidative stress caused by light and cold stress was used as the target gene to identify the most suitable internal control for normalizing real-time qRT-PCR. Two additional genes involved in the ABA biosynthesis pathway (NCED) and sugar metabolism (GS) were analyzed with the most stable internal control genes in order to check the results found with the ELIP gene. The expressions of UBC, a-TUB and EF1a were the most stable across acclimation and de-acclimation treatments. The expressions of the other housekeeping genes tested varied depending upon the conditions. The relative quantification of ELIP changed according to identities and the number of reference genes used, thus demonstrating the importance of selecting an appropriate number of reference genes in order to achieve an accurate and reliable normalization of gene expression during cold acclimation in E. globulus.