Metabolic Profiling of Sugars and Organic Acids, and Expression Analyses of Metabolism-Associated Genes in Two Yellow-Peel Pitaya Species.

Fangfang Xie,Guibing Hu,Jianye Chen,Jietang Zhao,Yonghua Qin,Canbin Chen,Jiaxuan Chen,Zhike Zhang,Qingzhu Hua,Yuanju Yuan

doi:10.3390/plants11050694

Abstract

Sugar and organic acids are important factors determining pitaya fruit quality. However, changes in sugars and acids, and expressions of metabolism-associated genes during fruit maturation of yellow-peel pitayas are not well-documented. In this study, metabolic and expression analyses in pulps of different fruit developmental stages of ‘Wucihuanglong’ (‘WCHL’, Hylocereus undatus) and ‘Youcihuanglong’ pitaya (‘YCHL’, Hylocereus megalanthus) were used to explore the sugar and organic acid metabolic process. Total phenols and flavonoids were mainly accumulated at S1 in pitaya pulps. Ascorbic acid contents of ‘WCHL’ pitaya were higher than that of ‘YCHL’ pitaya during fruit maturation. Starch was mainly accumulated at early fruit development stages while soluble sugars were rich in late stages. Sucrose, fructose, and glucose were the main sugar components of ‘YCHL’ pitaya while glucose was dominant in ‘WCHL’ pitaya. Malic and citric acids were the main organic acids in ‘WCHL’ and ‘YCHL’ pitayas, respectively. Based on the transcriptome analyses, 118 genes involved in pitaya sugar and organic acid metabolism were obtained. Results from the correlation analyses between the expression profiling of candidate genes and the contents of sugar and organic acid showed that 51 genes had a significant correlation relationship and probably perform key role in pitaya sugar and organic acid metabolism processes. The finding of the present study provides new information for quality regulation of pitayas.

Highlights

Introduction iationsPitaya belonging to Hylocereus genus within the Cactaceae family (Caryophyllales order) is native to Mexico, and Central and South America.Nowadays, pitayas are widely commercially cultivated in the tropical and subtropical regions
The change in total phenol, total flavonoid, and ascorbic acid contents were analyzed during fruit development of ‘WCHL’ and ‘YCHL’
Higher total phenol and flavonoid contents were detected in the stage 1 of yellow-peel pitaya pulps during fruit development

Summary

Introduction

Pitaya ( known as dragon fruit) belonging to Hylocereus genus within the Cactaceae family (Caryophyllales order) is native to Mexico, and Central and South America. Pitayas are widely commercially cultivated in the tropical and subtropical regions. Based on the color of peel and pulp, pitaya is mainly classified into three species, i.e., Hylocereus undatus (H. undatus, red or yellow peel with scales and white pulp), H. monacanthus or H. polyrhizus (red peel with scales and red pulp) and H. megalanthus or Selenicereus megalanthus (yellow peel without scales and with white pulp) [1]. Pitaya is popular with consumers due to its abundant betalains, exotic appearance, fresh and sweet taste, and high nutrients [2–4]. Yellow-peel pitayas have economic potential in the market due to its conspicuous appearance, shocking yellow color and long shelf life. Pitaya cultivars from a different genetic background have different biochemical and Licensee MDPI, Basel, Switzerland

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Conclusion