Modulation of CYP79 Genes and Glucosinolate Profiles in Arabidopsis by Defense Signaling Pathways

Abstract

Glucosinolates are natural plant products that function in the defense toward herbivores and pathogens. Plant defense is regulated by multiple signal transduction pathways in which salicylic acid (SA), jasmonic acid, and ethylene function as signaling molecules. Glucosinolate content was analyzed in Arabidopsis wild-type plants in response to single or combinatorial treatments with methyljasmonate (MeJA), 2,6-dichloro-isonicotinic acid, ethylene, and 2,4-dichloro-phenoxyacetic acid, or by wounding. In addition, several signal transduction mutants and the SA-depleted transgenic NahG line were analyzed. In parallel, expression of glucosinolate biosynthetic genes of the CYP79 gene family and the UDPG:thiohydroximate glucosyltransferase was monitored. After MeJA treatment, the amount of indole glucosinolates increased 3-to 4-fold, and the corresponding Trp-metabolizing genes CYP79B2 and CYP79B3 were both highly induced. Specifically, the indole glucosinolate N-methoxy-indol-3-ylmethylglucosinolate accumulated 10-fold in response to MeJA treatment, whereas 4-methoxy-indol-3-ylmethylglucosinolate accumulated 1.5-fold in response to 2,6-dichloro-isonicotinic acid. In general, few changes were seen for the levels of aliphatic glucosinolates, although increases in the levels of 8-methylthiooctyl glucosinolate and 8-methylsulfinyloctyl glucosinolate were observed, particularly after MeJA treatments. The findings were supported by the composition of glucosinolates in the coronatine-insensitive mutant coi1, the ctr1 mutant displaying constitutive triple response, and the SA-overproducing mpk4 and cpr1 mutants. The present data indicate that different indole glucosinolate methoxylating enzymes are induced by the jasmonate and the SA signal transduction pathways, whereas the aliphatic glucosinolates appear to be primarily genetically and not environmentally controlled. Thus, different defense pathways activate subsets of biosynthetic enzymes, leading to the accumulation of specific glucosinolates.Glucosinolates are amino acid-derived natural plant products that function in the defense against herbivores and microorganisms. Upon tissue disruption, e.g. caused by insect feeding, glucosinolates are hydrolyzed by specific thioglucosidases called myrosinases to produce an array of biologically active compounds, typically isothiocyanates, nitriles, and thiocyanates (for review, see Halkier, 1999;Rask et al., 2000). These compounds function as inhibitors of microbial growth (Mari et al., 1993;Manici et al., 1997), as attractants for specialist insects, and as deterrents of generalist herbivores. For humans, glucosinolates are important as flavor compounds, as cancer-preventive agents, and as biopesticides in agriculture.Glucosinolate biosynthesis is considered a threestep process: First, the amino acid may enter the chain elongation pathway, in which the condensing enzymes MAM1 and MAM-L have recently been identified (de Quiros et al., 2000;Kroymann et al., 2001). Second, the core glucosinolate structure is formed (see below); and t...

Intraspecific variation in defense against a generalist lepidopteran herbivore in populations of Eruca sativa (Mill.)

“…The regulation of GS in Arabidopsis is mainly governed by JA and its interaction with ethylene (Mikkelsen et al. 2003; Mewis et al. 2005, 2006), while SA signaling has been shown to suppress GS accumulation (Mewis et al.…”

Functional Analysis of the Tandem-Duplicated P450 Genes SPS/BUS/CYP79F1 and CYP79F2 in Glucosinolate Biosynthesis and Plant Development by Ds Transposition-Generated Double Mutants

“…It is unlikely that the higher cytokinin levels and the consequent developmental effects in these mutants is due to the higher indole glucosinolate levels, as the double mutants, despite their more extreme phenotypes, show comparable levels of indole glucosinolates to the single CYP79F1/sps mutant (Table I). A more likely possibility arises from the observation that the CYP79B2/B3 genes are up-regulated in stressed plants, resulting in increased indole glucosinolates and IAA (Mikkelsen et al, 2003). Therefore, it is also possible that sps/ cyp79F1 mutants are stressed because of the perturbation of cytokinin homeostasis, which in turn up-regulates CYP79B2/B3 genes.…”

Interaction between MYC2 and ETHYLENE INSENSITIVE3 Modulates Antagonism between Jasmonate and Ethylene Signaling inArabidopsis

“…However, such a synergistic regulatory model is inconsistent with the antagonistic roles of JA and ET signaling in many important processes. For example, JA antagonizes ET to repress apical hook formation (e.g., exaggerated hook formation in the coi1 mutant) (Figures 1 and 2) (Turner et al, 2002), whereas ET antagonizes JA to repress the expression of wound-responsive genes (VSP1, VSP2, and TAT3) and herbivore-inducible genes (CYP79B3, BCAT4, and BAT5) ( Figures 9A and 9B) (Rojo et al, 1999;Mikkelsen et al, 2003) and to attenuate plant defense against generalist herbivores ( Figures 9C and 9D) (Stotz et al, 2000;Mewis et al, 2005Mewis et al, , 2006Bodenhausen and Reymond, 2007).…”

“…In addition to their synergistic regulation, JA and ET also act antagonistically in regulating expression of wound-responsive genes (Rojo et al, 1999;Lorenzo et al, 2004) and metabolite biosynthetic genes (Mikkelsen et al, 2003). JA represses apical hook formation (Turner et al, 2002) and positively regulates plant defense against insect attack (Fernández-Calvo et al, 2011;Schweizer et al, 2013), while ET functions oppositely (Guzmán and Ecker, 1990;Mewis et al, 2005Mewis et al, , 2006Bodenhausen and Reymond, 2007).…”