Transcriptome Analysis Clarified Genes Involved in Betalain Biosynthesis in the Fruit of Red Pitayas (Hylocereus costaricensis)

Abstract

The red flesh trait gives red pitayas more healthful components and a higher price, while the genetic mechanism behind this trait is unknown. In this manuscript, transcriptome analysis was employed to discover the genetic differences between white and red flesh in pitayas. A total of 27.99 Gb clean data were obtained for four samples. Unigenes, 79,049 in number, were generated with an average length of 1333 bp, and 52,618 Unigenes were annotated. Compared with white flesh, the expression of 10,215 Unigenes was up-regulated, and 4853 Unigenes were down-regulated in red flesh. The metabolic pathways accounted for 64.6% of all differentially expressed Unigenes in KEGG pathways. The group with high betalain content in red flesh and all structural genes, related to betalain biosynthesis, had a higher expression in red flesh than white flesh. The expression of the key gene, tyrosine hydroxylase CYP76AD1, was up-regulated 245.08 times, while 4,5-DOPA dioxygenase DODA was up-regulated 6.46 times. Moreover, the special isomers CYP76AD1α and DODAα were only expressed in red flesh. The competitive anthocyanin biosynthesis pathway had a lower expression in red flesh. Two MYB transcription factors were of the same branch as BvMYB1, regulating betalain biosynthesis in beet, and those transcription factors had expression differences in two kinds of pitayas, which indicated that they should be candidate genes controlling betalain accumulation in red pitayas. This research would benefit from identifying the major gene controlling red flesh trait and breed new cultivars with the red flesh trait. Future research should aim to prove the role of each candidate gene in betalain biosynthesis in red pitayas.

Changes in carbohydrate metabolism and endogenous hormone regulation during bulblet initiation and development in Lycoris radiata

“…Only clean reads were used in subsequent analyses. The high-quality reads were assembled using Trinity with default parameters to construct unique consensus sequences [67,68].…”

Research Progress of Betalain in Response to Adverse Stresses and Evolutionary Relationship Compared with Anthocyanin

“…Other researchers have also conducted comprehensive and objective reviews on the biosynthesis, source and application of betalain pigments, especially on betalain biosynthesis [3,4,6,87,88], but excepting the aspect of assisting plant response to stresses and evolutionary relationship between betalains and anthocyanins, which provide a broad perspective on the currently used and potential new sources for betalains, including the use of natural resources or metabolic engineering and summing up the potential applications of betalains in research and business applications [4,23,62,89].…”

Combined Transcriptome and Metabolome analysis of Pitaya fruit unveiled the mechanisms underlying Peel and pulp color formation

“…Recently, the relatively low cost of Illumina sequencing has made it easier to perform global transcriptome profiling in any plant species. This helps us to understand the molecular mechanisms and key genes involved in defining key agronomic and quality traits [5,[21][22][23]. For example, tyrosine hydroxylase CYP76AD1 and 4,5-DOPA dioxygenase DODA, related to betalain biosynthesis, were identified as the key genes controlling the red pulp color of pitaya using the transcriptome approach [5].…”

“…This helps us to understand the molecular mechanisms and key genes involved in defining key agronomic and quality traits [5,[21][22][23]. For example, tyrosine hydroxylase CYP76AD1 and 4,5-DOPA dioxygenase DODA, related to betalain biosynthesis, were identified as the key genes controlling the red pulp color of pitaya using the transcriptome approach [5]. Non-targeted metabolome profiling is also a robust technique to understand the correlation between phenotypes and their metabolites [3,24].…”

“…Recently, metabolome profiling of pitaya demonstrated that the decrease of amino acid, accompanied by the increase of sugars and organic acid, might contribute to the formation of betalains [3]. Although few studies performed transcriptome or metabolome profiling of pitayas with either peel or pulp, none of the studies performed a combined transcriptome and metabolome analysis of both peel and pulp tissues of pitaya fruits to have a better understanding of key genes and metabolites involved in the peel and pulp color formation [2,3,5]. A detailed examination of the expression and accumulation of the key genes and metabolites underlying color formation in pitayas will facilitate the breeding of colorful cultivars with improved fruit appeal.…”