title: Identification of PAN2 by quantitative proteomics as a leucine-rich repeat-receptor-like kinase acting upstream of PAN1 to polarize cell division in maize.
abstract: Mechanisms governing the polarization of plant cell division are poorly understood. Previously, we identified pangloss1 (PAN1) as a leucine-rich repeat-receptor-like kinase (LRR-RLK) that promotes the polarization of subsidiary mother cell (SMC) divisions toward the adjacent guard mother cell (GMC) during stomatal development in maize (Zea mays). Here, we identify pangloss2 (PAN2) as a second LRR-RLK promoting SMC polarization. Quantitative proteomic analysis identified a PAN2 candidate by its depletion from membranes of pan2 single and pan1;pan2 double mutants. Genetic mapping and sequencing of mutant alleles confirmed the identity of this protein as PAN2. Like PAN1, PAN2 has a catalytically inactive kinase domain and accumulates in SMCs at sites of GMC contact before nuclear polarization. The timing of polarized PAN1 and PAN2 localization is very similar, but PAN2 acts upstream because it is required for polarized accumulation of PAN1 but is independent of PAN1 for its own localization. We find no evidence that PAN2 recruits PAN1 to the GMC contact site via a direct or indirect physical interaction, but PAN2 interacts with itself. Together, these results place PAN2 at the top of a cascade of events promoting the polarization of SMC divisions, potentially functioning to perceive or amplify GMC-derived polarizing cues.
authors.affiliation: Section of Cell and Developmental Biology, University of California at San Diego, La Jolla, California 92093, USA.
authors.forename: Xiaoguo
authors.initials: X
authors.lastname: Zhang
authors.forename: Michelle
authors.initials: M
authors.lastname: Facette
authors.forename: John A
authors.initials: JA
authors.lastname: Humphries
authors.forename: Zhouxin
authors.initials: Z
authors.lastname: Shen
authors.forename: Yeri
authors.initials: Y
authors.lastname: Park
authors.forename: Dena
authors.initials: D
authors.lastname: Sutimantanapi
authors.forename: Anne W
authors.initials: AW
authors.lastname: Sylvester
authors.forename: Steven P
authors.initials: SP
authors.lastname: Briggs
authors.forename: Laurie G
authors.initials: LG
authors.lastname: Smith
mesh_terms: D002455:Cell Division; D016764:Cell Polarity; D002874:Chromosome Mapping; D007930:Leucine; D000090263:Leucine-Rich Repeat Proteins; D008565:Membrane Proteins; D009154:Mutation; D010641:Phenotype; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D054046:Plant Stomata / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D040901:Proteomics; D020798:Two-Hybrid System Techniques; D003313:Zea mays / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000090263:Leucine-Rich Repeat Proteins; D008565:Membrane Proteins; D010940:Plant Proteins; D011506:Proteins; D010770:Phosphotransferases; D007930:Leucine