The roles of AaMIXTA1 in regulating the initiation of glandular trichomes and cuticle biosynthesis in Artemisia annua

Abstract

SummaryThe glandular secretory trichomes (GSTs) on Artemisia annua leaves have the capacity to secrete and store artemisinin, a compound which is the most effective treatment for uncomplicated malaria. An effective strategy to improve artemisinin content is therefore to increase the density of GSTs in A. annua. However, the formation mechanism of GSTs remains poorly understood.To explore the mechanisms of GST initiation in A. annua, we screened myeloblastosis (MYB) transcription factor genes from a GST transcriptome database and identified a MIXTA transcription factor, AaMIXTA1, which is expressed predominantly in the basal cells of GST in A. annua. Overexpression and repression of AaMIXTA1 resulted in an increase and decrease, respectively, in the number of GSTs as well as the artemisinin content in transgenic plants.Transcriptome analysis and cuticular lipid profiling showed that AaMIXTA1 is likely to be responsible for activating cuticle biosynthesis. In addition, dual-luciferase reporter assays further demonstrated that AaMIXTA1 could directly activate the expression of genes related to cuticle biosynthesis.Taken together, AaMIXTA1 regulated cuticle biosynthesis and prompted GST initiation without any abnormal impact on the morphological structure of the GSTs and so provides a new way to improve artemisinin content in this important medicinal plant.

Jasmonic acid‐responsive AabHLH1 positively regulates artemisinin biosynthesis in Artemisia annua

“…A). These tissues have abundant glandular trichomes, which are closely related with artemisinin biosynthesis . Additionally, AaADS showed high expression in the shoot, bud, and leaf, but low expression in the root, stem, and flower (Fig.…”

“…Artemisinin‐based combination therapies have been proposed by the World Health Organization as the best treatment for malaria . Artemisinin is produced in glandular secretory trichomes, which are mainly distributed in young leaves and buds of A. annua . The biosynthetic pathway of artemisinin has been almost completely elucidated in recent years .…”

A novel HD‐ZIP IV/MIXTA complex promotes glandular trichome initiation and cuticle development in Artemisia annua

“…In order to further investigate AaHD8 functions, we screened the cDNA library of A. annua young leaves for proteins interacting with AaHD8. Several proteins were identified, including a MYB transcription factor AaMIXTA1 which has been proven to be involved in regulating glandular trichome initiation and cuticle biosynthesis in A. annua by our group (Shi et al ., ). In further Y2H assays, AaHD8 strongly interacted with AaMIXTA1 (Fig.…”

“…Artemisia annua is well‐known for producing the antimalarial drug artemisinin, specifically synthesized in glandular trichomes, which makes it a suitable candidate plant for investigating the molecular mechanism of glandular trichome development (Graham et al ., ; Yan et al ., ). Previously, we demonstrated that the HD‐ZIP IV transcription factor AaHD1 and the MIXTA‐like protein AaMIXTA1 played important roles in promoting glandular trichome initiation in A. annua (Shi et al ., ; Yan et al ., ). AaMIXTA1 was identified to be a positive regulator of cuticle biosynthesis (Shi et al ., ).…”

“…Previously, we demonstrated that the HD‐ZIP IV transcription factor AaHD1 and the MIXTA‐like protein AaMIXTA1 played important roles in promoting glandular trichome initiation in A. annua (Shi et al ., ; Yan et al ., ). AaMIXTA1 was identified to be a positive regulator of cuticle biosynthesis (Shi et al ., ). HD‐ZIP IV and MIXTA‐like subfamily transcription factors are commonly regarded as the master regulators of epidermal cell fate and function in higher plants.…”