Local and systemic gene expression of sesquiterpene phytoalexin biosynthetic enzymes in plant leaves

Abstract

Production of antimicrobial metabolites known as phytoalexins is considered as one of the initial and main barriers to inhibit pathogen development in local infected aerial tissues. Capsidiol is the main bicyclic sesquiterpene phytoalexin in tobacco (Nicotiana tabacum) and chili pepper (Capsicum annuum). Production of 5-epi-aristolochene by the corresponding sesquiterpene cyclase enzymes is considered the critical step in capsidiol biosynthesis. To analyze the transcriptional activation of chili pepper 5-epi-aristolochene synthase gene expression in response to several pathogen-associated molecular patterns, a 1,455 bp promoter fragment upstream start codon was fully sequenced and fused to β-glucuronidase reporter gene. Analyses of spatial and temporal patterns of hybrid gene expression were carried out in transgenic tobacco plants. Surprisingly β-glucuronidase was detected in both, the locally treated and the phylotactically adjacent leaves. A particular systemic gene expression was localized in the immediate vascular tissue. The activation patterns of 5-epi-aristolochene synthase transcripts and detection of capsidiol in corresponding tobacco and pepper systemic leaves confirmed these results. This expression pattern might be mediated by reactive oxygen species. This is the first report of a highly localized systemic gene expression of enzymes directly involved in sesquiterpene phytoalexin biosynthesis in leaves, elicited by pathogen-associated molecular patterns.

Selection and validation of reference genes for studying stress-related agarwood formation of Aquilaria sinensis

“…Furthermore, the major compounds of resin are sesquiterpenes and chromones (Nakanishi et al 1981;Ishihara et al 1993;Yagura et al 2003). The former is a big group of plant natural terpene products, many of which have been classified as phytoalexins with antimicrobial or anti-insect activity (Banerjee et al 2006;Maldonado-Bonilla et al 2008;Gershenzon and Dudareva 2007). It is known that one of the major defensive mechanisms that plants developed during long process of evolution is providing physical and/or chemical barriers to hinder pathogen invasion before or after the wound or microbe attack (Yang et al 1997).…”

Defense gene expression in root galls induced by Nacobbus aberrans in CM334 chilli plants

“…It is well documented that several WRKY proteins regulate the expression of defense genes by binding to a consensus sequence known as W box [(T) GACC/T] in the promoter region of the target gene (Rushton et al, 2010). The W box is common in defense genes as those encoding for PRs and others defense genes such as EAS (5-epiaristolochene synthase) (Maldonado-Bonilla et al, 2008). Thus, in this study, the modulation of the WRK-a gene induced by N. aberrans and P. capsici in CM334 plant roots, perhaps favored the over-expression of defense genes WRKY-a, PR-1, POX and EAS in the incompatible interaction (Pc treatment) and its reduced expression in the compatible interaction (Na treatment).…”

Activity of the purified plant ABC transporter NtPDR1 is stimulated by diterpenes and sesquiterpenes involved in constitutive and induced defenses

“…Diterpenes are constitutively synthesized in, and secreted from, the head cells of glandular trichomes (61) where NtPDR1 is constitutively expressed (25). Capsidiol and other sesquiterpenes are synthesized as a response to pathogen attack in tissues next to the site of pathogen invasion (62,63). This is in agreement with the induced expression of the GUS reporter under the control of the NtPDR1 promoter in whole leaf tissues upon addition of the defense hormone methyl jasmonate, whereas expression was confined to the trichome secretory cells in the absence of this hormone.…”