The WRKY transcription factor HpWRKY44 regulates CytP450-like1 expression in red pitaya fruit (Hylocereus polyrhizus)

Abstract

Red pitaya (Hylocereus polyrhizus) fruit is a high-value, functional food, containing a high level of betalains. Several genes potentially related to betalain biosynthesis, such as cytochrome P450-like (CytP450-like), have been identified in pitaya fruit, while their transcriptional regulation remains unclear. In this work, the potential involvement of a WRKY transcription factor, HpWRKY44, in regulating CytP450-like1 expression in pitaya fruit was examined. HpWRKY44, a member of the Group 1 WRKY family, contains two conserved WRKY motifs and is localized in the nucleus. HpWRKY44 also exhibits trans-activation ability. Gene expression analysis showed that the expression of HpCytP450-like1 and HpWRKY44 increased steadily during pitaya fruit coloration, which corresponded with the production of elevated betalain levels in the fruit. HpWRKY44 was also demonstrated to directly bind to and activate the HpCytP450-like1 promoter via the recognition of the W-box element present in the promoter. Collectively, our findings indicate that HpWRKY44 transcriptionally activates HpCytP450-like1, which perhaps, at least in part, contributes to betalain biosynthesis in pitaya fruit. The information provided in the current study provides novel insights into the regulatory network associated with betalain biosynthesis during pitaya fruit coloration.

The evolution of betalain biosynthesis in Caryophyllales

“…At least one of these bHLH genes, ORF11 , is highly expressed in betacyanic tissue in S. oleracea , consistent with a role in betalain pigmentation (Cai et al ., ). Finally, a recent study has shown that a WRKY transcription factor, HpWRKY , identified by a RNAseq screen in the Hylocereus polyrhizus , can bind a W‐box motif present in the promoter of a CYP76AD1 homologue from the same species (Cheng et al ., ). WRKY transcription factors have more recently emerged as putative interacting partners with MBW complexes, controlling anthocyanin synthesis in both A. thaliana and Petunia hybrida (reviewed in Lloyd et al ., ).…”

MGH: a genome hub for the medicinal plant maca (Lepidium meyenii)

“…TFs such as the well-known WRKY ( 19 , 20 ) and basic leucine zipper (bZIP) ( 21 , 22 ) are proteins that control the transcription of a series of genes, thus are popular genes in both basic biology and applied breeding programs ( 23–26 ). The defining feature of TFs is that they contain at least one conserved DNA-binding domain that could bind to a specific corresponding DNA sequence, usually in the promoter region.…”

Constituent diversity of ethanol extracts from pitaya

“…Pitaya is named green dragon fruit 1 or red dragon fruit 2 . Originated in the tropics of Central America, 3 Taiwan Province of China began to introduce pitaya in early 1990s, 4 and in recent years, pitaya has been introduced to other provinces including Guangxi, Guangdong, Fujian, Yunnan, Hainan, and Guizhou 5 . The whole area of pitaya in China has an area of about 35–40 thousand hectares 6–8 .…”