Increased leaf angle1, a Raf-like MAPKKK that interacts with a nuclear protein family, regulates mechanical tissue formation in the Lamina joint of rice.
Mitogen-activated protein kinase kinase kinases (MAPKKKs), which function at the top level of mitogen-activated protein kinase cascades, are clustered into three groups. However, no Group C Raf-like MAPKKKs have yet been functionally identified. We report here the characterization of a rice (Oryza sativa) mutant, increased leaf angle1 (ila1), resulting from a T-DNA insertion in a Group C MAPKKK gene. The increased leaf angle in ila1 is caused by abnormal vascular bundle formation and cell wall composition in the leaf lamina joint, as distinct from the mechanism observed in brassinosteroid-related mutants. Phosphorylation assays revealed that ILA1 is a functional kinase with Ser/Thr kinase activity. ILA1 is predominantly resident in the nucleus and expressed in the vascular bundles of leaf lamina joints. Yeast two-hybrid screening identified six closely related ILA1 interacting proteins (IIPs) of unknown function. Using representative IIPs, the interaction of ILA1 and IIPs was confirmed in vivo. IIPs were localized in the nucleus and showed transactivation activity. Furthermore, ILA1 could phosphorylate IIP4, indicating that IIPs may be the downstream substrates of ILA1. Microarray analyses of leaf lamina joints provided additional evidence for alterations in mechanical strength in ila1. ILA1 is thus a key factor regulating mechanical tissue formation at the leaf lamina joint.
National Key Laboratory of Crop Genetic Improvement and National Center for Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan, China.
Jing
J
Ning
Baocai
B
Zhang
Nili
N
Wang
Yihua
Y
Zhou
Lizhong
L
Xiong
D000595:Amino Acid Sequence; D001696:Biomechanical Phenomena; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D003001:Cloning, Molecular; D019295:Computational Biology; D004789:Enzyme Activation; D005816:Genetic Complementation Test; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012275:Oryza / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D010766:Phosphorylation; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D058526:Plant Vascular Bundle / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015533:Transcriptional Activation; D020798:Two-Hybrid System Techniques
D009687:Nuclear Proteins; D010940:Plant Proteins; D020930:MAP Kinase Kinase Kinases