Lupeol Accumulation Correlates with Auxin in the Epidermis of Castor

Abstract

Lupeol, a natural lupane-type pentacyclic triterpene, possesses various pharmacological properties, and its production attracts attention. Significant quantities of lupeol are deposited on the castor aerial organ surface and are easily extractable as a predominant wax constituent. Thus, castor might be considered as a potential bioreactor for the production of lupeol. The lupeol biosynthesis pathway is well known, but how it is regulated remains largely unknown. Among large numbers of castor cultivars, we targeted one accession line (337) with high levels of lupeol on its stem surface and low levels thereof on its hypocotyl surface, implicating that lupeol synthesis is differentially regulated in the two organs. To explore the underlying mechanisms, we did comparative transcriptome analysis of the first internode of 337 stem and the upper hypocotyl. Our results show that large amounts of auxin-related genes are differentially expressed in both parts, implying some possible interactions between auxin and lupeol production. We also found that several auxin-responsive cis-elements are present in promoter regions of HMGR and LUS genes encoding two key enzymes involved in lupeol production. Furthermore, auxin treatments apparently induced the expression levels of RcHMGR and RcLUS. Furthermore, we observed that auxin treatment significantly increased lupeol contents, whereas inhibiting auxin transport led to an opposite phenotype. Our study reveals some relationships between hormone activity and lupeol synthesis and might provide a promising way for improving lupeol yields in castor.

Genome-Wide Identification and In Silico Analysis of ZF-HD Transcription Factor Genes in Zea mays L.

“…Except for tomatoes, our findings imply that ZF-HD/ZHD family genes have been largely conserved in evolution, along with their functions. In previous studies of ZF-HD/ZHD genes in other plants, researchers have concluded that these genes have undergone severe purifying selection, and their functions cannot be differentiated [ 42 , 48 , 49 , 50 , 51 , 52 ]. Motif analysis showed various conserved motifs of ZmZHD proteins in Classes I and II, revealing similar motifs present in the same subclass in the phylogenetic tree that are functionally similar ( Figure 3 A,C).…”

Natural products of pentacyclic triterpenoids: from discovery to heterologous biosynthesis

“…Wang et al 217 revealed the ultrahigh production of oleanolic acid in the shoot of Achyranthes bidentata of 371.8 mg L −1 , a 5.4-fold increase compared to the control after 2 days treatment of 0.2 mM MeJA, while the AbHMGR gene was expressed at a higher level, which suggested that oleanolic acid production may be the result of the up-regulated expression of AbHMGR . Additionally, auxin, 218 SA, 219 and GA 220 were also reported to regulate the HMGR gene, thus affecting the biosynthesis of pentacyclic triterpenoids. FPS is a key enzyme that regulates the synthesis of terpenoid precursors such as IPP and DMAPP in the MVA pathway.…”

Opportunities and Challenges of Castor Bean (Ricinus communis L.) Genetic Improvement

“…A transcriptome analysis showed that several auxin-related genes have different patterns of expression in the hypocotyl, characterized by a low level of lupeol, and stem internodes, with a high level of lupeol, suggesting that auxin might be implied in the regulation of lupeol biosynthesis. Furthermore, several auxin-responsive cis-elements are found in promoter regions of two key enzymes involved in lupeol production (RcHMGR and RcLUS), of which the expression seemed to be induced by auxin treatments, and lupeol content was reported to be increased by auxin treatment and decreased by auxin transport inhibition [120]. Wang et al [121] have identified a glutathione peroxidase gene family in the genome of R. communis.…”