The MKK7-MPK6 MAP Kinase Module Is a Regulator of Meristem Quiescence or Active Growth in Arabidopsis

Abstract

Plant growth flexibly adapts to environmental conditions. Growth initiation itself may be conditional to a suitable environment, while the most common response of plants to adverse conditions is growth inhibition. Most of our understanding about environmental growth inhibition comes from studies on various plant hormones, while less is known about the signaling mechanisms involved. The mitogen-activated protein kinase (MAPK) cascades are central signal transduction pathways in all eukaryotes and their roles in plant stress responses is well-established, while increasing evidence points to their involvement in hormonal and developmental processes. Here we show that the MKK7-MPK6 module is a suppressor of meristem activity using genetic approaches. Shoot apical meristem activation during light-induced de-etiolation is accelerated in mpk6 and mkk7 seedlings, whereas constitutive or induced overexpression of MKK7 results in meristem defects or collapse, both in the shoot and the root apical meristems. These results underscore the role of stress-activated MAPK signaling in regulating growth responses at the whole plant level, which may be an important regulatory mechanism underlying the environmental plasticity of plant development.

Nitrogen Starvation Differentially Influences Transcriptional and Uptake Rate Profiles in Roots of Two Maize Inbred Lines with Different NUE

“…Different actors can play a role in the signal transduction at the basis of these Lo5-specific root responses such as kinases. Interestingly, an increase in expression levels of a transcript ( GRMZM2G344388_T01 , Table S3) encoding a protein showing homology to AtMKK7 belonging to the MKK7-MKK6 module, a suppressor of meristem activity [39], can be linked to the hypothesized reduction of root growth in Lo5 under N starvation. Besides, the upregulation of the homologous to the Arabidopsis mitogen-activated protein kinase phosphatase PP2C5 ( GRMZM2G077187_T01 , Table S3) reinforces this hypothesis.…”

Nitrogen starvation reveals the mitotic potential of mutants in the S/MAPK pathways

“…In several filamentous fungi spore germination is controlled by light, and phytochrome mutants working upstream of the MAP kinase SakA germinate faster than wild-type 44 . In Arabidopsis, the MAPK mpk6 mutant promotes exit from quiescence of the shoot apical meristem 45 . In human and mouse muscles, p38/Sty1 inhibition promotes the proliferation of quiescent satellite cells 46 .…”

Receptor-Like Protein Kinases Function Upstream of MAPKs in Regulating Plant Development

“…Overexpression of MKK7 leads to collapsed and defective SAM. The process of de-etiolation induced by light is enhanced in the mkk7 and mpk6 mutants, suggesting that MKK7 and MPK6 function as negative regulators of meristem activity [ 36 ]. The CLAVATA-WUSCHEL (CLV-WUS) feedback loop is the classic regulatory pathway that maintains the homeostasis of the SAM [ 184 , 185 ].…”

“…NaMEK2 regulates pollen germination and wound response in Nicotiana attenuata [ 34 ]. AtMKK7, a group D MAPKK, was reported to control plant development and stress response [ 35 , 36 , 37 ]. Plant MAPKKKs are classified into three groups (A–C) by homology of the kinase domain.…”