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Abstract
Developmental flexibility under stress conditions largely relies on the interactions between hormones that mediate stress responses and developmental processes. In this study, we showed that the stress hormone jasmonic acid (JA) induces formation of extra xylem in the roots of wild-type Arabidopsis thaliana (Col-0). JA signaling mutants such as coronatine insensitive1-1 and jasmonate resistant1-1 did not form extra xylem in response to JA, but the JA biosynthesis mutant oxophytodienoate-reductase3 did form extra xylem. These observations suggested that the JA response promotes xylem development. To understand the mechanism, we examined the regulatory interaction between JA and cytokinin, a negative regulator of xylem development. JA treatment reduced cytokinin responses in the vasculature, and exogenous cytokinin nullified the effect of JA on formation of extra xylem. A time-course experiment showed that suppression of cytokinin responses by JA does not occur rapidly, but the JA-mediated xylem phenotype is tightly linked to the suppression of the cytokinin response. Further analysis of arabidopsis histidine phosphotransfer protein6-1 and myc2-3 mutants revealed that the JA-responsive transcription factor MYC2 regulates the expression of AHP6 in response to JA and expression of AHP6 is involved in the JA-mediated xylem phenotype.
Highlights
Molecular and genetic studies have identified many phytohormones and have shown that the activities of these hormones largely overlap, each hormone has specific signaling pathways that act non-redundantly
To understand the regulatory interaction between jasmonic acid (JA) and cytokinin, we examined root growth in Col-0 plants treated with JA, cytokinin, or both (Fig. 1a; see Supplementary Fig. S1)
Developmental flexibility under stress conditions largely occurs via the interaction between hormones that mediate stress responses and developmental processes
Summary
Molecular and genetic studies have identified many phytohormones and have shown that the activities of these hormones largely overlap, each hormone has specific signaling pathways that act non-redundantly. Tomato DC3000, Botrytis cinerea, and Fusarium oxysporum compared to wild-type plants, and JA-mediated inhibition of root growth is suppressed in myc[2] mutant plants[14, 15] These observations suggest that MYC2 regulates the expression of key genes responsible for the modulation of defense and development in response to JA. Chen et al showed that apical root growth inhibition by JA is caused by the suppression of proliferative activity in root meristematic cells, and MYC2 regulates www.nature.com/scientificreports/. This process by repressing expression of the auxin-responsive gene PLETHORA, which is responsible for stem cell maintenance and cell division[25]. These observations suggested that cytokinin is a negative regulator of xylem development[28, 29]
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