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The role of MYB34, MYB51 and MYB122 in the regulation of camalexin biosynthesis in Arabidopsis thaliana.

Frerigmann H, Glawischnig E, Gigolashvili T - Front Plant Sci (2015)

Bottom Line: The abundance of camalexin was strongly reduced in myb34/51 and myb51/122 double and in triple myb mutant, suggesting that these transcription factors are important in camalexin biosynthesis.Furthermore, expression of MYB51 and MYB122 was significantly increased by biotic and abiotic camalexin-inducing agents.In conclusion, this study reveals the importance of MYB factors regulating the generation of IAOx as precursor of camalexin.

View Article: PubMed Central - PubMed

Affiliation: Botanical Institute and Cluster of Excellence on Plant Sciences, University of Cologne, Cologne Germany.

ABSTRACT
The phytoalexin camalexin and indolic glucosinolates share not only a common evolutionary origin and a tightly interconnected biosynthetic pathway, but regulatory proteins controlling the shared enzymatic steps are also modulated by the same R2R3-MYB transcription factors. The indolic phytoalexin camalexin is a crucial defense metabolite in the model plant Arabidopsis. Indolic phytoalexins and glucosinolates appear to have a common evolutionary origin and are interconnected on the biosynthetic level: a key intermediate in the biosynthesis of camalexin, indole-3-acetaldoxime (IAOx), is also required for the biosynthesis of indolic glucosinolates and is under tight control by the transcription factors MYB34, MYB51, and MYB122. The abundance of camalexin was strongly reduced in myb34/51 and myb51/122 double and in triple myb mutant, suggesting that these transcription factors are important in camalexin biosynthesis. Furthermore, expression of MYB51 and MYB122 was significantly increased by biotic and abiotic camalexin-inducing agents. Feeding of the triple myb34/51/122 mutant with IAOx or indole-3-acetonitrile largely restored camalexin biosynthesis. Conversely, tryptophan could not complement the low camalexin phenotype of this mutant, which supports a role for the three MYB factors in camalexin biosynthesis upstream of IAOx. Consistently expression of the camalexin biosynthesis genes CYP71B15/PAD3 and CYP71A13 was not negatively affected in the triple myb mutant and the MYBs could not activate pCYP71B15::uidA expression in trans-activation assays with cultured Arabidopsis cells. In conclusion, this study reveals the importance of MYB factors regulating the generation of IAOx as precursor of camalexin.

No MeSH data available.


Silver nitrate induces the transcription of MYB51 and MYB122 as well as that of CYP71B15 and CYP71A13. The expression of camalexin biosynthesis genes (CYP71B15 and CYP71A13) and of MYB34, MYB51, and MYB122 upon silver nitrate (AgNO3) treatment is shown. The relative expression in Col-0 was measured in leaves of 6-week-old plants 18 h after treatment (MOCK = 1). Data are means ± SE from four independent experiments each with two to three biological replicates (n = 11). Values marked with asterisks are significantly different from those of control plants (Student’s t-test; p < 0.05).
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Figure 2: Silver nitrate induces the transcription of MYB51 and MYB122 as well as that of CYP71B15 and CYP71A13. The expression of camalexin biosynthesis genes (CYP71B15 and CYP71A13) and of MYB34, MYB51, and MYB122 upon silver nitrate (AgNO3) treatment is shown. The relative expression in Col-0 was measured in leaves of 6-week-old plants 18 h after treatment (MOCK = 1). Data are means ± SE from four independent experiments each with two to three biological replicates (n = 11). Values marked with asterisks are significantly different from those of control plants (Student’s t-test; p < 0.05).

Mentions: To further validate the importance of R2R3-MYBs in camalexin regulation, we analyzed the induction of MYB34, MYB51, and MYB122 in response to elicitors of camalexin production. In a pilot experiment, we treated Arabidopsis Col-0 WT plants with AgNO3, a commonly used abiotic elicitor of camalexin induction, which strongly induced CYP71B15, CYP71A13, MYB122, and MYB51 (Figure 2). However, the expression of MYB34 was reduced, indicating that it plays a less important role in phytoalexin regulation.


The role of MYB34, MYB51 and MYB122 in the regulation of camalexin biosynthesis in Arabidopsis thaliana.

Frerigmann H, Glawischnig E, Gigolashvili T - Front Plant Sci (2015)

Silver nitrate induces the transcription of MYB51 and MYB122 as well as that of CYP71B15 and CYP71A13. The expression of camalexin biosynthesis genes (CYP71B15 and CYP71A13) and of MYB34, MYB51, and MYB122 upon silver nitrate (AgNO3) treatment is shown. The relative expression in Col-0 was measured in leaves of 6-week-old plants 18 h after treatment (MOCK = 1). Data are means ± SE from four independent experiments each with two to three biological replicates (n = 11). Values marked with asterisks are significantly different from those of control plants (Student’s t-test; p < 0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4548095&req=5

Figure 2: Silver nitrate induces the transcription of MYB51 and MYB122 as well as that of CYP71B15 and CYP71A13. The expression of camalexin biosynthesis genes (CYP71B15 and CYP71A13) and of MYB34, MYB51, and MYB122 upon silver nitrate (AgNO3) treatment is shown. The relative expression in Col-0 was measured in leaves of 6-week-old plants 18 h after treatment (MOCK = 1). Data are means ± SE from four independent experiments each with two to three biological replicates (n = 11). Values marked with asterisks are significantly different from those of control plants (Student’s t-test; p < 0.05).
Mentions: To further validate the importance of R2R3-MYBs in camalexin regulation, we analyzed the induction of MYB34, MYB51, and MYB122 in response to elicitors of camalexin production. In a pilot experiment, we treated Arabidopsis Col-0 WT plants with AgNO3, a commonly used abiotic elicitor of camalexin induction, which strongly induced CYP71B15, CYP71A13, MYB122, and MYB51 (Figure 2). However, the expression of MYB34 was reduced, indicating that it plays a less important role in phytoalexin regulation.

Bottom Line: The abundance of camalexin was strongly reduced in myb34/51 and myb51/122 double and in triple myb mutant, suggesting that these transcription factors are important in camalexin biosynthesis.Furthermore, expression of MYB51 and MYB122 was significantly increased by biotic and abiotic camalexin-inducing agents.In conclusion, this study reveals the importance of MYB factors regulating the generation of IAOx as precursor of camalexin.

View Article: PubMed Central - PubMed

Affiliation: Botanical Institute and Cluster of Excellence on Plant Sciences, University of Cologne, Cologne Germany.

ABSTRACT
The phytoalexin camalexin and indolic glucosinolates share not only a common evolutionary origin and a tightly interconnected biosynthetic pathway, but regulatory proteins controlling the shared enzymatic steps are also modulated by the same R2R3-MYB transcription factors. The indolic phytoalexin camalexin is a crucial defense metabolite in the model plant Arabidopsis. Indolic phytoalexins and glucosinolates appear to have a common evolutionary origin and are interconnected on the biosynthetic level: a key intermediate in the biosynthesis of camalexin, indole-3-acetaldoxime (IAOx), is also required for the biosynthesis of indolic glucosinolates and is under tight control by the transcription factors MYB34, MYB51, and MYB122. The abundance of camalexin was strongly reduced in myb34/51 and myb51/122 double and in triple myb mutant, suggesting that these transcription factors are important in camalexin biosynthesis. Furthermore, expression of MYB51 and MYB122 was significantly increased by biotic and abiotic camalexin-inducing agents. Feeding of the triple myb34/51/122 mutant with IAOx or indole-3-acetonitrile largely restored camalexin biosynthesis. Conversely, tryptophan could not complement the low camalexin phenotype of this mutant, which supports a role for the three MYB factors in camalexin biosynthesis upstream of IAOx. Consistently expression of the camalexin biosynthesis genes CYP71B15/PAD3 and CYP71A13 was not negatively affected in the triple myb mutant and the MYBs could not activate pCYP71B15::uidA expression in trans-activation assays with cultured Arabidopsis cells. In conclusion, this study reveals the importance of MYB factors regulating the generation of IAOx as precursor of camalexin.

No MeSH data available.