Project description:Pineapple is a non climacteric fruit. This study investigates changes in gene expression between the mature green fruit and mature yellow fruit ripening stages
Project description:DNA methylation is a conserved epigenetic mark that influences diverse biological processes in many eukaryotes. Recently, DNA methylation was proposed to regulate fleshy fruit ripening. Fleshy fruits can be distinguished by their ripening process as climacteric fruits, such as tomatoes, or non-climacteric fruits, such as strawberries. Tomatoes undergo a global decrease in DNA methylation during ripening, due to increased expression of a DNA demethylase gene. The dynamics and biological relevance of DNA methylation during ripening of non-climacteric fruits, or other climacteric fruits, are unknown. Here, we generated and characterized single-base resolution maps of the DNA methylome in strawberry fruit, from immature to ripe stages. We observed an overall loss of DNA methylation during strawberry fruit ripening. Thus, ripening-induced DNA hypomethylation occurs not only in climacteric fruit, but also in non-climacteric fruit. However, we discovered that the mechanisms underlying DNA hypomethylation during ripening of tomato and strawberry are distinct. Unlike in tomatoes, DNA demethylase genes were not up-regulated during ripening of strawberries. Instead, genes involved in RNA-directed DNA methylation were down-regulated during strawberry ripening. Further, ripening-induced DNA hypomethylation was associated with decreased siRNA levels, consistent with reduced RdDM activity. Therefore, we propose that DNA hypomethylation during strawberry ripening is caused by diminished RdDM activity. Finally, hundreds of ripening-related genes displayed altered expression that was associated with, and thus potentially regulated by, DNA hypomethylation during ripening. Our findings provide new insight into the DNA methylation dynamics during the ripening of non-climateric fruit and reveal a novel function of RdDM in regulating an important process in plant development.
Project description:The Capsicum genus shows remarkable phenotypic diversity, making it an excellent system to study non-climacteric fruit ripening. Unlike climacteric model species, such as tomato (Solanum lycopersicum), the regulatory networks linking transcriptome and metabolome to fruit quality traits remain poorly understood in non-climacteric crop species. To address this gap, we selected four contrasting C. chinense accessions and performed integrated transcriptomic and metabolomic analyses to investigate the regulation of total soluble solids (TSS) accumulation. We profiled 16,922 genes and 63 metabolic features across two fruit developmental stages (immature and mature), including sugars, organic acids, capsaicinoids, and other secondary metabolites. We identified more than 3,800 differentially expressed genes and detected strong correlations between gene expression and metabolite levels. Some metabolites, including chlorophylls, carotenoids, and starch, showed consistent temporal trends across genotypes, while others showed genotype-dependent variation. Our results demonstrate that pepper fruit ripening involves a transcriptional shift toward soluble sugar accumulation, characterized by upregulation of starch-hydrolyzing enzymes (CaAMY1/2, CaBAM1), invertases (CaINV1, CaCWINV3), sucrose synthase (CaSUS2), and the sugar transporter CaSWEET10, alongside downregulation of the starch biosynthetic gene CaSBE1. Among these, CaSUS2, CaSWEET10 and CaBAM1 emerged as key candidate regulators. These results suggest that coordinated starch degradation and sucrose transport primarily drive TSS increase, while secondary metabolism undergoes substantial changes during ripening but does not appear to be a major contributor to this process.
Project description:In contrast to climacteric fruits such as tomato, the knowledge on key regulatory genes controlling the ripening of strawberry, a non-climacteric fruit, is still limited. NAC transcription factors mediate different developmental processes in plants. Here, we identified and characterized FaRIF (Ripening Inducing Factor), a NAC transcription factor that is highly expressed and induced in strawberry receptacles during ripening. Functional analyses based on stable transgenic lines aimed at silencing FaRIF by RNA interference, either from a constitutive promoter or the ripe receptacle-specific EXP2 promoter, as well as overexpression lines showed that FaRIF controls critical ripening-related processes such as fruit softening and pigment and sugar accumulation. Physiological, metabolome and transcriptome analyses of receptacles of FaRIF-silenced and overexpression lines point to FaRIF as a key regulator of strawberry fruit ripening from early developmental stages, controlling abscisic acid (ABA) biosynthesis and signaling, cell wall degradation and modification, the phenylpropanoid pathway, volatiles production, and the balance of the aerobic/anaerobic metabolism. FaRIF is therefore a target to be modified/edited to control the quality of strawberry fruits.