Os06g0724900

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Annotated Information

ILA1 is a functional kinase with Ser/Thr kinase activity.

Function

ILA1 is a functional kinase with Ser/Thr kinase activity.ILA1 is a key factor regulating mechanical tissue formation at the leaf lamina joint and is involved in mechanical tissue formation in the leaf lamina joint[1].

Expression

ILA1 is predominantly resident in the nucleus and expressed in the vascular bundles of leaf lamina joints.ILA1Encodes a Group C Raf-Like MAPKKK with Ser/Thr Kinase Activity[2].Thermal asymmetric interlaced PCR show that the increased leaf angle ofila1arises from a T-DNA insertion in Os06g50920.Because nuclear localization is a significant feature of transcription factors, GFP is fused to the N terminus of IIP2 and IIP4 and transformed the rice protoplasts. Detection of thefusion proteins in the nuclei of the transformed cells suggest that IIP2 and IIP4 are nuclear-localized proteins. To confirm the sequence identity ofILA1, a complementation test is performed by transforming theila1 mutant with an 8.8-kbgenomic region that included the complete open reading frame(ORF) and putative promoter region for ILA1 (pILA1). All of the complementation lines show the wild-type leaf inclination,suggesting that Os06g50920 is ILA1.The leaf angle of WT is increased compared that of ila1. But the increased leaf angle of ila1 is not due to altered BR.ILA1 mutation significantly represses the expression of genes involved in cell wall synthesis and consequently causes the increased leaf responses [3].ILA1 regulates mechanical strength in the leaf lamina joint.Genome-wide exploration of the expression profiles of ila1 and wild-type leaf lamina joints showed that the expressionof many genes involved in cell wall formation is downregulated in the mutants.Rice leaf angle is one of the important agronomic traits affecting plant architecture and yield. Most of the previously documented rice leaf inclination mutants arise from BR-induced cell division and/or elongation at the adaxial surface of the leaf lamina joint. Suppression of BR biosynthesis or signaling generally blocks cell propagation/expansion and results in an erect leaf; in the presence of BR, cell division/expansion occurs and induces an increased leaf angle[4].

ILA1 encodes a putative MAPKKK protein with a length of 564 amino acids and a molecular mass of 63 kD. According to the Pfam database, the deduced ILA1 has an N-terminal ACT domain (PF01842) and a C-terminal kinase domain (PF07714), which likely confer a protein regulatory feature and kinase activity, respectively. Sequence alignment of ILA1 with several identified MAPKKKs from three representative plant species reveal that the characteristic features for MAPKKK proteins, including all of the 11 subdomains and a Lys in the ATP binding site, are highly conserved in ILA1. ILA1 represents a potentially unique paradigm in the regulation of leaf angle in rice. QRT-PCR analysis reveal high expression levels of ILA1 in both leaves and leaf lamina joints. However,ila1 exhibits a visible phenotype mainly in its leaf lamina joints butnot in its leaves. To confirm the interaction of ILA1 with IIPs, the ILA1 protein is split into kinase (ILA1K) and regulatory (ILA1R) domains andsubjected to interaction analysis.The kinase domain of ILA1 is involved in the interaction with IIPs in subfamily B, but not with IIPs in subfamily A.And the N-terminal regulatory domain interacts with IIPs. 

 IIPs,the likely targets of ILA1, are nuclear proteins with ransactivation activity.In light of the evidence for interaction between ILA1 and IIPs, it seemed that IIPs may be the phosphorylated substrates of ILA1.IIP4 is selected  as a representative to test this hypothesis.IIP4 fused to a polyhistidine tag (His-IIP4)is purified and incubated

with GST-ILA1 for an in vitro kinase activity assay. Radioactively labeled IIP4 is detected. These results reveal that IIP4 is a phosphorylated substrate of ILA1, as is likely the case for the other IIPs.The Gene Ontology database annotate IIPs as putative transcription factors.

Evolution

ILA1 is a raf-like MAPKKK of Group C.ILA1 encodes a putative MAPKKK protein with a length of 564 amino acids and a molecular mass of 63 kD.The deduced ILA1 has an N-terminal ACT domain (PF01842) and a C-terminal kinase domain (PF07714), which likely confer a protein regulatory feature and kinase activity, respectively. Sequence alignment of ILA1 with several identified MAPKKKs from three representative plant species reveal that the characteristic features for MAPKKK proteins, including all of the 11 subdomains and a Lys in the ATP binding site, are highly conserved in ILA1. You can also add sub-section(s) at will. The increased leaf angle of ila1 is not due to altered BR. The increased leaf inclination cosegregated with the homozygous T-DNA insertion based on PCR analysis.RT-PCR assays show that the intact transcript ofOs06g50920 is undetectable in the ila1 mutant,indicating that the T-DNA insertion nearly represses expression of the targeted gene.BR-induced rice leaf inclination often results from rapid expansion and propagation of collar adaxial cells.Scanning electron microscopy is used to observe the adaxial surface and longitudinal sections ofial1 and wild-type leaf lamina joints. No significant alterations in cell expansion and propagation are found in the adaxial region.So the increased leaf angle of ila1 is not due to altered BR. Possible mechanism of ILA1 action Identification of ILA1 phosphorylation substrates is critical for understanding the signal transduction pathway of a Group C Raflike MAPKKK member. Through yeast two-hybrid screening of the cDNA library, six interaction proteins (IIPs) were found; these IIPs consist of a small family with unknown functions. The interactions were further confirmed by the BiFC and Co-IP analyses of a representative IIP. More importantly,ILA1 could phosphorylate an IIP in vitro. IIPs are thus likely to be the authentic downstream targets of ILA1. IIPs may act as transcription factors for they were regarded as putative transcription factors by bioinformatic analysis;they are nuclear localized in rice and they showed transactivation activity in yeast. In fact, direct phosphorylation of a transcription factor by a MAPKKK has been previously reported[5]. Many transcription factors have been found that are involved in modulating rice leaf inclination. Most of them act through BR signaling pathways [6].Some, not related to BR responses, also function in cell division or expansion.[7]As the interacting proteins of ILA1, IIPs appear to regulate directly or indirectly multiple aspects of cell wall–related gene expression in the leaf lamina joint.

Labs working on this gene

  1. National Key Laboratory of Crop Genetic Improvement and National Center for Plant Gene Research (Wuhan), Huazhong

Agricultural University, Wuhan , China

  1. State Key Laboratory of Plant Genomics and National Centre for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing , China
  2. Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia
  3. Department of Plant Biology, University of Georgia, Athens, Georgia
  4. Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
  5. Disease Resistance Research Unit,Plant Genome Research Unit (S.K.),National Institute of Agrobiological Sciences, Tsukuba,Japan
  6. Graduate School of Science and Technology, Tokyo University of Science, Noda, Japan (A.T., T.K.)
  7. Institute of Society for Techno-Innovation of Agriculture,Forestry and Fisheries,Tsukuba, Japan (Z.S.)
  8. Faculty of Agriculture, Utsunomiya University, Utsunomiya,Japan (C.T., H.S.)
  9. Department of Bioscience, Teikyo University, Utsunomiya 320–8551, Japan (T.N., T.Y.);
  10. Department of Applied Biological Chemistry, University of Tokyo,Tokyo, Japan (T.A.)

References

  1. ↑ Jing Ning;Baocai Zhang;Nili Wang;Yihua Zhou;Lizhong Xiong (2011).Increased Leaf Angle1,a Raf-Like MAPKKK That Interacts with a Nuclear Protein Family, Regulates Mechanical Tissue Formation in the Lamina Joint of Rice.The Plant Cell,23(12): 4334-4347.
  2. ↑ Eichberg J.,and Iyer, S.(1996). Phosphorylation of myelin protein:Recent advances. Neurochem. Res.21:527–535.3.
  3. ↑ Wang,L.,Xie,W.,Chen,Y.,Tang,W.,Yang,J.,Ye,R.,Liu,L.,Lin,Y.,Xu, C., Xiao, J.,and Zhang,Q.(2010).A dynamic gene expression atlas covering the entire life cycle of rice. Plant J.61:752–766.
  4. ↑ Sakamoto T.,et al.(2006). Erect leaves caused by brassinosteroid deficiency increase biomass production and grain yield in rice. Nat.Biotechnol.24:105–109.
  5. ↑ Miao,Y., Laun, T.M., Smykowski, A., and Zentgraf, U.(2007).Arabidopsis MEKK1 can take a short cut: It can directly interact with senescence-related WRKY53 transcription factor on the protein level and can bind to its promoter. Plant Mol. Biol. 65:63–76.
  6. ↑ Lee, S., Choi, S.C., and An, G.(2008). Rice SVP-group MADS-box proteins, OsMADS22 and OsMADS55, are negative regulators of brassinosteroid responses. Plant J.54:93–105. Cite error: Invalid <ref> tag; name "ref6" defined multiple times with different content Cite error: Invalid <ref> tag; name "ref6" defined multiple times with different content Cite error: Invalid <ref> tag; name "ref6" defined multiple times with different content
  7. ↑ Zhao, S.Q., Hu, J., Guo, L.B., Qian, Q., and Xue, H.W.(2010). Rice leaf inclination2, a VIN3-like protein, regulates leaf angle through modulating cell division of the collar. Cell Res. 20:935–947.

Structured Information

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