MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate （IG） biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redund...MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate （IG） biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redundantly convert tryptophan to indole-3-acetaldoxime （IAOx）. This intermediate represents a branching point for IG biosynthesis, and pathways leading to camalexin and indole-carboxylic acids （ICA）. Here we investigate how these MYBs affect the pathogen-triggered Trp metabolism. Our experiments indicated that these three MYBs affect not only IG production but also constitutive biosynthesis of other IAOx- derived metabolites. Strikingly, the PENETRATION 2 （PEN2）-dependent IG-metabolism products, which are absent in myb34/51/122 and pen2 mutants, were indispensable for full flg22-mediated induction of other IAOx-dedved compounds. However, germ induction and accumulation of ICAs and camalexin upon path- ogen infection was not compromised in myb34/51/122 plants, despite strongly reduced IG levels. Hence, in comparison with cyp79B2/B3, which lacks all IAOx-derived metabolites, we found myb34/51/122 an ideal tool to analyze IG contribution to resistance against the necrotrophic fungal pathogen Plectosphaerella cucumerina. The susceptibility of myb34/51/122 was similar to that of pen2, but much lower than susceptibility of cyp79B2/B3, indicating that MYB34/51/122 contribute to resistance toward P. cucumerina exclu- sively through IG biosynthesis, and that PEN2 is the main leaf myrosinase activating IGs in response to microbial pathogens.展开更多
Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two...Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two different plant cellular compartments has divergent effects on the plant transcriptome. Arabidopsis thaliana overexpressing glycolate oxidase in the chloroplast （Fahnenstich et al., 2008; Balazadeh et al., 2012） and plants deficient in peroxisomal catalase （Queval et al., 2007; Inze et al., 2012） were grown under non-photorespiratory conditions and then transferred to photorespiratory conditions to foster the production of H202 in both organelles. We show that H202 originating in a specific organelle induces two types of responses： one that integrates signals independently from the subcellular site of H202 production and another that is dependent on the H2O2 production site. H2O2 produced in peroxisomes induces transcripts involved in protein repair responses, while H2O2 produced in chloroplasts induces early signaling responses, including transcription factors and biosynthetic genes involved in production of secondary signaling messengers. There is a significant bias towards the induction of genes involved in responses to wounding and pathogen attack by chloroplas- tic-produced H202, including indolic glucosinolates-, camalexin-, and stigmasterol-biosynthetic genes. These transcriptional responses were accompanied by the accumulation of 4-methoxy-indol-3-ylmethyl glucosinolate and stigmasterol.展开更多
文摘MYB34, MYB51, and MYB122 transcription factors are known as decisive regulators of indolic glucosinolate （IG） biosynthesis with a strong impact on expression of genes encoding CYP79B2 and CYP79B3 enzymes that redundantly convert tryptophan to indole-3-acetaldoxime （IAOx）. This intermediate represents a branching point for IG biosynthesis, and pathways leading to camalexin and indole-carboxylic acids （ICA）. Here we investigate how these MYBs affect the pathogen-triggered Trp metabolism. Our experiments indicated that these three MYBs affect not only IG production but also constitutive biosynthesis of other IAOx- derived metabolites. Strikingly, the PENETRATION 2 （PEN2）-dependent IG-metabolism products, which are absent in myb34/51/122 and pen2 mutants, were indispensable for full flg22-mediated induction of other IAOx-dedved compounds. However, germ induction and accumulation of ICAs and camalexin upon path- ogen infection was not compromised in myb34/51/122 plants, despite strongly reduced IG levels. Hence, in comparison with cyp79B2/B3, which lacks all IAOx-derived metabolites, we found myb34/51/122 an ideal tool to analyze IG contribution to resistance against the necrotrophic fungal pathogen Plectosphaerella cucumerina. The susceptibility of myb34/51/122 was similar to that of pen2, but much lower than susceptibility of cyp79B2/B3, indicating that MYB34/51/122 contribute to resistance toward P. cucumerina exclu- sively through IG biosynthesis, and that PEN2 is the main leaf myrosinase activating IGs in response to microbial pathogens.
文摘Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two different plant cellular compartments has divergent effects on the plant transcriptome. Arabidopsis thaliana overexpressing glycolate oxidase in the chloroplast （Fahnenstich et al., 2008; Balazadeh et al., 2012） and plants deficient in peroxisomal catalase （Queval et al., 2007; Inze et al., 2012） were grown under non-photorespiratory conditions and then transferred to photorespiratory conditions to foster the production of H202 in both organelles. We show that H202 originating in a specific organelle induces two types of responses： one that integrates signals independently from the subcellular site of H202 production and another that is dependent on the H2O2 production site. H2O2 produced in peroxisomes induces transcripts involved in protein repair responses, while H2O2 produced in chloroplasts induces early signaling responses, including transcription factors and biosynthetic genes involved in production of secondary signaling messengers. There is a significant bias towards the induction of genes involved in responses to wounding and pathogen attack by chloroplas- tic-produced H202, including indolic glucosinolates-, camalexin-, and stigmasterol-biosynthetic genes. These transcriptional responses were accompanied by the accumulation of 4-methoxy-indol-3-ylmethyl glucosinolate and stigmasterol.
