Abstract
Plant mitogen-activated protein kinase (MAPK) cascades play important roles in development and stress responses. In previous studies, we have systematically investigated the mitogen-activated protein kinase kinase (MKK) and MAPK gene families in cotton. However, the complete interactions between MAPK gene family members in MAPK signaling cascade is poorly characterized. Herein, we investigated the mitogen-activated protein kinase kinase kinase (MAPKKK) family members and identified a total of 89 MAPKKK genes in the Gossypium raimondii genome. We cloned 51 MAPKKKs in G. hirsutum and investigated the interactions between MKK and MAPKKK proteins through yeast-two hybrid assays. A total of 18 interactive protein pairs involved in 14 MAPKKKs and six MKKs were found. Among these, 13 interactive pairs had not been reported previously. Gene expression patterns revealed that 12 MAPKKKs were involved in diverse signaling pathways triggered by hormone treatments or abiotic stresses. By combining the MKK-MAPK and MKK-MAPKKK protein interactions with gene expression patterns, 38 potential MAPK signaling modules involved in the complicated cross-talks were identified, which provide a basis on elucidating biological function of the MAPK cascade in response to hormonal and/or stress responses. The systematic investigation in MAPK signaling cascades will lay a foundation for understanding the functional roles of different MAPK cascades in signal transduction pathways, and for the improvement of various defense responses in cotton.
Highlights
Mitogen-activated protein kinase (MAPK) cascades play central roles in the signaling pathways that transduce extracellular stimuli into intracellular responses in eukaryotes[1,2,3]
MEKK1-MKK1/2-MPK4 cascade is involved in responses to cold, salt and pathogen infection[18,19]; MAPKKK17/18-MKK3-MPK1/2/7/14 cascade is an abscisic acid (ABA) dependent mitogen-activated protein kinase (MAPK) pathway and plays a role in ABA stress signaling[31]; YDA-MKK4/5-MPK3/6 module is involved in the regulation of stomatal development[21]; and the ANP3-MKK6-MPK4 cascade participates in male-specific meiotic cytokinesis[20]
We identified 89 mitogen-activated protein kinase kinase kinase (MAPKKK) genes in G. raimondii, and found that segmental duplication played a central role in the expansion of the MAPKKK family in the G. raimondii genome
Summary
Mitogen-activated protein kinase (MAPK) cascades play central roles in the signaling pathways that transduce extracellular stimuli into intracellular responses in eukaryotes[1,2,3]. As the first components of MAPK cascades, MAPKKKs phosphorylate and activate MKKs, MKKs phosphorylate MAPKs, and MAPKs can phosphorylate a wide range of substrates, such as transcription factors, kinases and cytoskeleton associated proteins These signaling cascades have frequent crosstalk to allow plants to regulate both development and stress tolerance[5]. MEKK1-MKK1/2-MPK4 cascade is involved in responses to cold, salt and pathogen infection[18,19]; MAPKKK17/18-MKK3-MPK1/2/7/14 cascade is an abscisic acid (ABA) dependent MAPK pathway and plays a role in ABA stress signaling[31]; YDA-MKK4/5-MPK3/6 module is involved in the regulation of stomatal development[21]; and the ANP3-MKK6-MPK4 cascade participates in male-specific meiotic cytokinesis[20]. This work lays a solid foundation to better understand the molecular mechanisms regulated by MAPK cascades in cotton, and to be utilized for the improvement of cotton responses to stress in breeding
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