Project description:A transcriptome analysis was applied on two peach (Prunus persica L.) cultivars with different sensitivity to low temperature regimes to identify cold-responsive genes that might be involved in tolerance to long low temperature storage. Peach fruit from ‘Morettini No2’ and ‘Royal Glory’, a sensitive and a tolerant, to chilling injury cultivars, respectively, were harvested at commercial maturity stage and allowed to ripen at room temperature (25°C) or subjected to 4 and 6-weeks of cold storage (0°C, 95% R.H.) followed by ripening at room temperature. Microarray experiments, employing the peach microarray platform (μ PEACH 1.0), were carried out by comparing harvested fruit against 4- and 6-week cold-stored fruit. The analysis identified 173 and 313 genes that were differentially expressed in ‘Morettini No2’ and ‘Royal Glory’ fruit after 4 weeks, respectively. However, the 6 weeks cold storage provoked a decrease in the total number of genes differentially expressed in both cultivars. RNA blot analysis validated the differential expression of certain genes showed in microarray data. Among these genes, two heat shock proteins (hsps), a putative β-D-xylosidase, an expansin, a dehydrin and a pathogenesis-related protein PR-4B precursor were induced during cold storage in both cultivars. The induction of hsps and the putative β-D-xylosidase appeared to be independent on the duration of postharvest treatment. On the other hand, transcript levels of lipoxygenase were quite constant during postharvest ripening, while a strong reduction or disappearance was observed after cold storage. A dehydration-induced RD22-like protein showed a reduction in the accumulation of transcripts during postharvest ripening independently on the temperature conditions. Overall, the current study shed some light on the molecular aspects of cold stress in peach fruit quality and identified some ripening and/or cold-induced genes which function need further elucidation.
Project description:Spring frost is a growing risk to temperate fruit production as warmer winter conditions can lead to earlier bloom, increasing the chance of damaging cold temperatures. One strategy to minimize the impacts of frost is to breed late-flowering cultivars to avoid the frost risk period. In this study, we analyzed Late-Flowering Peach (LFP) germplasm and showed its floral buds require longer chilling and warming periods during dormancy than the control cultivar, ‘John Boy’ (JB). We identified a 983-bp deletion in an AP2 gene, dubbed euAP2a, present only in LFP but not in 14 other peach genomes analyzed. This mutation eliminates an miR172 binding site, possibly allowing the euAP2a transcript to accumulate preferentially during chilling. These findings together with an early report that a deletion in the same euAP2a causes increasing floral petals, a morphological mark that also occurs in LFP, implies that the 983-bp deletion may contribute to the late-flowering phenotype. Furthermore, RNAseq data revealed that that two chilling- and three warm-responsive co-expression modules, which were collectively composed of 2,931 genes, were differentially activated at four of 13 dormancy stages. This activation was concurrent with a transient, stage-specific down-regulation of euAP2a. However, the mutated euAP2a in LFP did not exhibit the periodic downregulation events observed in JB and the concurrent activation of the five modules, leading to potential loss of activation of two chilling-responsive modules and an 8–12-day delay of three warm-responsive modules, which corresponds to the longer chilling requirement and delayed flowering time in the LFP buds. These findings support euAP2a as a potential regulator to control both floral development and bloom time in peach. Our findings provide important insight into the mechanisms underlying flowering time in peach, as well as a novel regulatory pathway that may operate in other plants. The results provide new insights to facilitate the breeding of new cultivars with late-flowering frost-avoidance traits.
Project description:We performed small RNA deep sequencing and identified 47 peach-specific and 47 known miRNAs or families with distinct expression patterns. Together, the identified miRNAs targeted 80 genes, many of which have not been reported previously. Like the model plant systems, peach has two of the three conserved trans-acting siRNA biogenesis pathways with similar mechanistic features and target specificity. Unique to peach, three of the miRNAs collectively target 49 MYBs, 19 of which are known to regulate phenylpropanoid metabolism, a key pathway associated with stone hardening and fruit color development, highlighting a critical role of miRNAs in regulation of peach fruit development and ripening. We also found that the majority of the miRNAs were differentially regulated in different tissues, in part due to differential processing of miRNA precursors. Up to 16% of the peach-specific miRNAs were differentially processed from their precursors in a tissue specific fashion, which has been rarely observed in plant cells. The miRNA precursor processing activity appeared not to be coupled with its transcriptional activity but rather acted independently in peach. Collectively, the data characterizes the unique expression pattern and processing regulation of peach miRNAs and demonstrates the presence of a complex, multi-level miRNA regulatory network capable of targeting a wide variety of biological functions, including phenylpropanoid pathways which play a multifaceted spatial-temporal role in peach fruit development. Identification of peach miRNAs and their targets from four different tissues
Project description:We performed small RNA deep sequencing and identified 47 peach-specific and 47 known miRNAs or families with distinct expression patterns. Together, the identified miRNAs targeted 80 genes, many of which have not been reported previously. Like the model plant systems, peach has two of the three conserved trans-acting siRNA biogenesis pathways with similar mechanistic features and target specificity. Unique to peach, three of the miRNAs collectively target 49 MYBs, 19 of which are known to regulate phenylpropanoid metabolism, a key pathway associated with stone hardening and fruit color development, highlighting a critical role of miRNAs in regulation of peach fruit development and ripening. We also found that the majority of the miRNAs were differentially regulated in different tissues, in part due to differential processing of miRNA precursors. Up to 16% of the peach-specific miRNAs were differentially processed from their precursors in a tissue specific fashion, which has been rarely observed in plant cells. The miRNA precursor processing activity appeared not to be coupled with its transcriptional activity but rather acted independently in peach. Collectively, the data characterizes the unique expression pattern and processing regulation of peach miRNAs and demonstrates the presence of a complex, multi-level miRNA regulatory network capable of targeting a wide variety of biological functions, including phenylpropanoid pathways which play a multifaceted spatial-temporal role in peach fruit development.
Project description:The fruit of melting-flesh peach cultivars produce high levels of ethylene caused by high expression of PpACS1, resulting in rapid fruit softening at the late-ripening stage. In contrast, the fruit of stony hard peach cultivars do not soften and produce little ethylene due to low expression of PpACS1. To elucidate the mechanism for suppressing PpACS1 expression in stony hard peaches, a microarray analysis was performed. Several genes that displayed similar expression patterns as PpACS1 were identified and shown to be IAA-inducible genes. Change in gene expression according to growth of fruits in 'melting peach M-bM-^@M-^XAkatsukiM-bM-^@M-^Y fruit sampled at 92, 98, 104 and 106 day after full bloom (DAB). Propylene induced gene expression stony peach M-bM-^@M-^XManamiM-bM-^@M-^Y and M-bM-^@M-^XOdorokiM-bM-^@M-^Y harvested at commercial maturity (Tatsuki et al., 2006).