Dataset Information

Transcriptome and Metabolome Analyses Provide Insights into the Occurrence of Peel Roughing Disorder on Satsuma Mandarin (Citrus unshiu Marc.) Fruit.

ABSTRACT: Roughing disorder (RD) is a significant quality barrier in citrus fruit, prevalent on easy-peeling mandarins. As RD is not yet well-understood, this study aimed to examine the changes and synergic molecular processes involved in peel RD. Peel with RD was induced by severely defruiting Satsuma mandarin trees. Morphology observations, RNA-sequencing, and targeted and untargeted metabolic analyses were conducted. The results showed that the primary metabolites of sugars, organic acids and amino acids are dramatically changed in RD peel. The RD peel was always characterized by higher magnesium content during development. Comparative transcriptome profiling was performed for CK and RD peels at 30, 80, and 170 days after full bloom (DAFB) which represented fruit at cell division stage, cell enlargement stage and fruit maturity stage, respectively. Physiological and molecular biological evidence suggested that the month after full bloom is a crucial stage for RD initiation. A total of 4,855 differentially expressed genes (DEGs) in RD peel, relative to CK peel were detected at cell division stage, about 2 to 4-fold more than other stages had. Among the differentially expressed transcription factors, the bHLH family were affected most by RD, and six bHLH transcription factors functionally involved in GA metabolism were assessed to associate with RD occurrence. Gene set enrichment analysis suggested that RD significantly altered starch and GA metabolism in peel. Higher starch content and hydrolysed chain status were found in RD peel at cell division stage. RD occurrence on the peel was influenced significantly by GA, especially abundant GA before July. These changes may mean a significant alteration in sink strength of RD peel. The findings of this study provide insights into the emergence, development and molecular mechanisms of RD.

SUBMITTER: Lu XP

PROVIDER: S-EPMC5682035 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Transcriptome and Metabolome Analyses Provide Insights into the Occurrence of Peel Roughing Disorder on Satsuma Mandarin (<i>Citrus unshiu</i> Marc.) Fruit.

Lu Xiao-Peng XP Li Fei-Fei FF Xiong Jiang J Cao Xiong-Jun XJ Ma Xiao-Chuan XC Zhang Zi-Mu ZM Cao Shang-Yin SY Xie Shen-Xi SX

Frontiers in plant science 20171107

Roughing disorder (RD) is a significant quality barrier in citrus fruit, prevalent on easy-peeling mandarins. As RD is not yet well-understood, this study aimed to examine the changes and synergic molecular processes involved in peel RD. Peel with RD was induced by severely defruiting Satsuma mandarin trees. Morphology observations, RNA-sequencing, and targeted and untargeted metabolic analyses were conducted. The results showed that the primary metabolites of sugars, organic acids and amino aci ...[more]

PMID: 29163622

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Project description:Peel degreening is the most conspicuous aspect of fruit ripening in many citrus fruits because of its importance for marketability. In this study, peel degreening in response to propylene (an ethylene analog) and at varying storage temperatures was characterized in Satsuma mandarin (Citrus unshiu Marc.) fruit. Propylene treatment triggered rapid peel degreening (within 4–6 days), indicated by an increase in the citrus color index (CCI) and chlorophyll loss. Peel degreening was also observed in fruit at 10°C and 15°C after 28–42 days, with gradual CCI increase and chlorophyll reduction. However, fruit at 5°C, 20°C, and 25°C remained green, and no substantial changes in peel CCI and chlorophyll content were recorded during the 42-day storage duration. The transcriptomes of peels of fruit treated with propylene for 4 days and those stored at varying temperatures for 28 days were then analyzed by RNA-Seq. We identified three categories of differentially expressed genes that were regulated by (i) propylene (and by analogy, ethylene) alone, (ii) low temperature (5°C, 10°C, or 15°C vs. 25°C) alone, and (iii) either propylene or low temperature. Gene-encoding proteins associated with chlorophyll degradation (such as CuSGR1, CuNOL, CuACD2, CuCAB2, and CuLHCB2) and a transcription factor (CuERF114) were differentially expressed by propylene or low temperature. To further examine temperature-induced pathways, we also monitored gene expression during on-tree fruit maturation vs. postharvest. The onset of on-tree peel degreening coincided with autumnal drops in field temperatures, and it was accompanied by differential expression of low temperature-regulated genes. On the contrary, genes that were exclusively regulated by propylene (such as CuCOPT1 and CuPOX-A2) displayed insignificant expression changes during on-tree peel degreening. These findings indicate that low temperatures could be involved in the fruit ripening-related peel degreening independently of ethylene.

Project description:Fructophilic lactic acid bacteria (FLAB), composed of Fructobacillus spp., Lactobacillus kunkeei, and Lactobacillus apinorum, are unique in that they prefer d-fructose over d-glucose as a carbon source. Strain F192-5, isolated from the peel of a satsuma mandarin and identified as Leuconostoc citreum, grows well on d-fructose but poorly on d-glucose and produces mainly lactate and acetate, with trace amounts of ethanol, from the metabolism of d-glucose. These characteristics are identical to those of obligate FLAB. However, strain F192-5 ferments a greater variety of carbohydrates than known FLAB. Comparative analyses of the genomes of strain F192-5 and reference strains of L. citreum revealed no signs of specific gene reductions, especially genes involved in carbohydrate transport and metabolism, in the genome of F192-5. The bifunctional alcohol/acetaldehyde dehydrogenase gene (adhE) is conserved in strain F192-5 but is not transcribed. This is most likely due to a deletion in the promoter region upstream of the adhE gene. Strain F192-5 did, however, ferment d-glucose when transformed with a plasmid containing the allochthonous adhE gene. L. citreum F192-5 is an example of a pseudo-FLAB strain with a deficiency in d-glucose metabolism. This unique phenotypic characteristic appears to be strain specific within the species L. citreum This might be one of the strategies lactic acid bacteria use to adapt to diverse environmental conditions.IMPORTANCE Obligate fructophilic lactic acid bacteria (FLAB) lack the metabolic pathways used in the metabolism of most carbohydrates and differ from other lactic acid bacteria in that they prefer to ferment d-fructose instead of d-glucose. These characteristics are well conserved at the genus or species level. Leuconostoc citreum F192-5 shows similar growth characteristics. However, the strain is metabolically and genomically different from obligate FLAB. This is an example of a strain that evolved a pseudo-FLAB phenotype to adapt to a fructose-rich environment.

Dataset Information

Transcriptome and Metabolome Analyses Provide Insights into the Occurrence of Peel Roughing Disorder on Satsuma Mandarin (Citrus unshiu Marc.) Fruit.

Publications

Transcriptome and Metabolome Analyses Provide Insights into the Occurrence of Peel Roughing Disorder on Satsuma Mandarin (<i>Citrus unshiu</i> Marc.) Fruit.

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