Transcriptomic and Gas Chromatography–Mass Spectrometry Metabolomic Profiling Analysis of the Epidermis Provides Insights into Cuticular Wax Regulation in Developing ‘Yuluxiang’ Pear Fruit

Abstract

The layer of cuticular wax covering fruits plays important roles in protecting against disease, preventing nonstomatal water loss, and extending shelf life. However, the molecular basis of cuticular wax biosynthesis in pear (Pyrus) fruits remains elusive. Our study thoroughly investigates cuticular wax biosynthesis during pear fruit development from morphologic, transcriptomic, and gas chromatography−mass spectrometry metabolomic perspectives. Our results showed that cuticular wax concentrations increased during the early stage [20−80 days after full bloom (DAFB)] from 0.64 mg/cm 2 (50 DAFB) to 1.75 mg/cm 2 (80 DAFB) and then slightly decreased to 1.22 mg/cm 2 during the fruit ripening period (80−140 DAFB). Scanning electron microscopy imaging indicated that wax plate crystals increased and wax structures varied during the pear fruit development. The combined transcriptomic and metabolomic profiling analysis revealed 27 genes, including 12 genes encoding transcription factors and a new structural gene (Pbr028523) encoding β-amyrin synthase, participating in the biosynthesis, transport, and regulation of cuticular wax according to their expression patterns in pear fruit. The quantitative real-time polymerase chain reaction experiments of 18 differentially expressed genes were performed and confirmed the accuracy of the RNA-Seq-derived transcript expression. A model of VLCFAs and cuticular wax synthesis and transport in pear fruit is proposed, providing a mechanistic framework for understanding cuticular wax biosynthesis in pear fruit. These results and data sets provide a foundation for the molecular events related to cuticular wax in 'Yuluxiang' pear fruit and may also help guide the functional analyses of candidate genes important for improving the cuticular wax of pear fruit in the future.

Unravelling Plant Responses to Stress—The Importance of Targeted and Untargeted Metabolomics

“…Changes within the structure of callose, in response to stress, could also be assessed through multistage LC-MS/MS and MS n , as well as 2D NMR post purification. Long-chain cuticular waxes have been classically analyzed with GC-MS [ 58 , 59 ] and, recently, ToF-SIMS has also been applied to the spatial analysis of leaf cuticular wax distributions [ 60 ].…”

Effect of 1-methylcyclopropene on peel greasiness, yellowing, and related gene expression in postharvest ‘Yuluxiang’ pear

“…It has been shown that the CAC1 and CAC3 genes in apple, the CAC gene in the ‘Newhall’ orange mutant glossy, and two homologs of the PbrCAC1 gene in ‘Yuluxiang’ pear are involved in the biosynthesis of VLCFA n ≤ 18 in wax ( Liu et al., 2015 ; Yang et al., 2017a ; Wu et al., 2019 ). Here the expression levels of CAC3 and CAC3L were consistent with the changes in the amounts of two fatty acids (C16 and C18:1) in fruit wax ( Figures 4 , 8 ), and both genes were down-regulated by 1-MCP.…”

Gas Chromatography–Mass Spectrometry Metabolite Analysis Combined with Transcriptomic and Proteomic Provide New Insights into Revealing Cuticle Formation during Pepper Development

“…The cuticle formation is a complex biological process, involving the synthesis and transportation of fatty acids and their derivatives. Until now, the wax and cutin synthesis pathway and related genes have been clearly found in model organisms Arabidopsis and tomato. − In addition, relevant research has also been carried out in apples, pears, citrus, etc., but is still incomplete. During the process of fruit development, due to the expansion of volume and the change of shape, it is often accompanied by dynamic changes in the cuticle composition.…”

“…These changes are bound to be associated with gene expression. It was found that the wax concentration first increased and then decreased during the development of pears, and 12 genes encoding transcription factors and a new gene encoding β-amyrin synthesis were revealed . For ‘Newhall’ navel orange ( Citrus sinensis Osbeck), wax synthesis was synchronized with fruit ripening under the effect of transcription factor GL1-like .…”

“…It was found that the wax concentration first increased and then decreased during the development of pears, and 12 genes encoding transcription factors and a new gene encoding β-amyrin synthesis were revealed. 10 For 'Newhall' navel orange (Citrus sinensis Osbeck), wax synthesis was synchronized with fruit ripening under the effect of transcription factor GL1-like. 11 Currently, the research on pepper cuticle is only on the composition of wax and cutin monomer among different pepper varieties.…”