A MAPK cascade in signaling lateral root emergence

【作者】 徐娟；

【机构】 浙江大学生命科学学院；

【摘要】 Mitogen-activated protein kinase(MAPK,or MPK) cascades are highly conserved signaling modules downstream of receptors/sensors that transduce extracellular stimuli into intracellular responses in eukaryotes.Arabidopsis MPK3 and MPK6,two closely related MAPKs,are involved in signaling multiple defense responses and play essential roles in plant growth and development including embryogenesis,oval development,stomatal differentiation,pollen development,abscission,localized cell division,and plant morphogenesis.The multi-functionality of this cascade can be attributed to the spatiotemporal expression of upstream ligand-receptor pairs and downstream MAPK substrates.Lateral root(LR) emergence is a highly coordinated process involving precise cell-cell communication.Here we show that MPK3 and MPK6,and their common upstream MAPKKs,MKK4 and MKK5,function downstream of HAESA(HAE)/HAESA-LIKE2(HSL2) and their ligand INFLORESCENCE DEFICIENT IN ABSCISSION(IDA) during LR emergence.Loss of function of MKK4/MKK5 or MPK3/MPK6 resulted in restricted passage of the growing LR primordia(LRPs) through the overlaying endodermal,cortical,and epidermal cell layers,leading to reduced LR density.MKK4/MKK5-MPK3/MPK6 module regulates the expression of cell wall remodeling(CWR) genes in the cells overlaying LRPs,therefore,controls the pectin degradation in the middle lamella.Expression of constitutively active MKK4 or MKK5 driven by HAE or HSL2 promoter fully rescues the LR emergence defect in ida and hae hsl2 mutants.In addition,the MKK4/MKK5-MPK3/MPK6 module is indispensable in auxin-facilitated LR emergence.Our study provides new insights into the auxin-governed and IDA-HAE/HLS2 ligand-receptor pair-mediated LR emergence process.更多还原

【Abstract】 Mitogen-activated protein kinase(MAPK,or MPK) cascades are highly conserved signaling modules downstream of receptors/sensors that transduce extracellular stimuli into intracellular responses in eukaryotes.Arabidopsis MPK3 and MPK6,two closely related MAPKs,are involved in signaling multiple defense responses and play essential roles in plant growth and development including embryogenesis,oval development,stomatal differentiation,pollen development,abscission,localized cell division,and plant morphogenesis.The multi-functionality of this cascade can be attributed to the spatiotemporal expression of upstream ligand-receptor pairs and downstream MAPK substrates.Lateral root(LR) emergence is a highly coordinated process involving precise cell-cell communication.Here we show that MPK3 and MPK6,and their common upstream MAPKKs,MKK4 and MKK5,function downstream of HAESA(HAE)/HAESA-LIKE2(HSL2) and their ligand INFLORESCENCE DEFICIENT IN ABSCISSION(IDA) during LR emergence.Loss of function of MKK4/MKK5 or MPK3/MPK6 resulted in restricted passage of the growing LR primordia(LRPs) through the overlaying endodermal,cortical,and epidermal cell layers,leading to reduced LR density.MKK4/MKK5-MPK3/MPK6 module regulates the expression of cell wall remodeling(CWR) genes in the cells overlaying LRPs,therefore,controls the pectin degradation in the middle lamella.Expression of constitutively active MKK4 or MKK5 driven by HAE or HSL2 promoter fully rescues the LR emergence defect in ida and hae hsl2 mutants.In addition,the MKK4/MKK5-MPK3/MPK6 module is indispensable in auxin-facilitated LR emergence.Our study provides new insights into the auxin-governed and IDA-HAE/HLS2 ligand-receptor pair-mediated LR emergence process.更多还原