TcMYB29a, an ABA-Responsive R2R3-MYB Transcriptional Factor, Upregulates Taxol Biosynthesis in Taxus chinensis

Abstract

Paclitaxel (Taxol), a highly modified diterpene agent mainly obtained from Taxus species, is the most widely used anticancer drug. Abscisic acid (ABA) is a well-known stress hormone that plays important roles in the secondary metabolism of plants, and it can also induce the accumulation of taxol in Taxus cell suspension cultures. However, the mechanism behind the regulation of taxol biosynthesis by ABA remains largely unknown. In previous research, a R2R3 MYB transcription factor (TF) TcMYB29a was observed to show a significant correlation with taxol biosynthesis, indicative of its potential role in the taxol biosynthesis. In this study, the TcMYB29a encoded by its gene was further characterized. An expression pattern analysis revealed that TcMYB29a was highly expressed in the needles and roots. Overexpression of TcMYB29a in Taxus chinensis cell suspension cultures led to an increased accumulation of taxol, and upregulated expression of taxol-biosynthesis-related genes, including the taxadiene synthase (TS) gene, the taxane 5α-hydroxylase (T5OH) gene, and the 3′-N-debenzoyl-2′-deoxytaxol-N-benzoyltransferase (DBTNBT) gene as compared to the controls. Chromatin immunoprecipitation (ChIP) assays, yeast one-hybrid (Y1H) assays, electrophoretic mobility shift assays (EMSAs), and dual-luciferase reporter assays verified that TcMYB29a could bind and activate the promoter of TcT5OH. Promoter sequence analysis of TcMYB29a revealed that its promoter containing an AERB site from -313 to -319 was a crucial ABA-responsive element. Subsequently, the ABA treatment assay showed that TcMYB29a was strongly upregulated at 6 h after ABA pretreatment. Furthermore, TcMYB29a was strongly suppressed at 3 h after the methyl jasmonate (MeJA) treatment and was depressed to the platform at 12 h. Taken together, these results reveal that TcMYB29a is an activator that improves the accumulation of taxol in Taxus chinensis cells through an ABA-medicated signaling pathway which is different from JA-medicated signaling pathways for the accumulation of taxol. These findings provide new insights into the potential regulatory roles of MYBs on the expression of taxol biosynthetic genes in Taxus.

Integrated mass spectrometry imaging and single‐cell transcriptome atlas strategies provide novel insights into taxoid biosynthesis and transport in Taxus mairei stems

“…The taxol biosynthesis pathway is controlled by several environmental and genetic factors (Feng et al., 2023; Yu et al., 2020; Yu et al., 2022; Zhan et al., 2022). Recent studies on taxol biosynthesis regulators mainly focused on stimulus‐responsive TFs (Cao et al., 2022; Chen, Zhang, et al., 2021; Zhang et al., 2015). We provided a single‐cell perspective on novel TF screening, which was consistent with cell‐specific expression patterns of taxol biosynthesis pathway genes.…”

“…Previously, the roles of T. media MYB39 / MYB3 and T. chinensis MYB29a in regulating taxol biosynthesis were identified (Cao et al., 2022; Yu et al., 2022). Our downstream target screening showed several different TF–target pairs, such as TmMYB3– TS , TmMYB3– TBT , TmMYB39– GGPPS , TmMYB39– T10OH , and TcMYB29a– T5OH .…”

“…In Taxus media , the MYB39–bHLH13 TF complex has key roles in the sexual dimorphic accumulation of taxol (Yu et al., 2022). In Taxus chinensis , MYB29a is an activator of abscisic acid (ABA)‐mediated taxol biosynthesis and WRKY33 is a repressor of salicylic acid (SA)‐mediated taxol biosynthesis (Cao et al., 2022; Chen, Zhang, et al., 2021). While progress has been made in the TF‐mediated regulation of taxol biosynthesis, the regulatory networks underpinning taxol biosynthesis require more investigation.…”

Functional Characterization of Myb Gene in Rice

“…Several MYB genes enhance drought stress response by controlling abscisic acid (ABA) signal (Ding et al, 2009;Seo et al, 2009 andCao et al, 2022). AtMYB15 displayed higher tolerance to salinity through enhanced sensitivity to abscisic acid (Ding et al, 2009).…”

The upstream regulatory mechanism of BplMYB46 and the function of upstream regulatory factors that mediate resistance to stress in Betula platyphylla

“…The MYB family is one of the largest families of TFs in plants; MYB TFs play key roles in primary and secondary metabolism and regulate resistance to biotic and abiotic stresses and other physiological processes in plants ( Mitra et al., 2019 ; Berardi et al., 2021 ; Xiao et al., 2021 ; Cao et al., 2022 ). Over expression of MYB6 in transgenic poplar up-regulates the expression of flavonoid biosynthesis genes and significantly increases the accumulation of anthocyanins and proanthocyanidins in Populus tomentosa ( Wang et al., 2019 ).…”