title: The juxtamembrane and carboxy-terminal domains of Arabidopsis PRK2 are critical for ROP-induced growth in pollen tubes.
abstract: Polarized growth of pollen tubes is a critical step for successful reproduction in angiosperms and is controlled by ROP GTPases. Spatiotemporal activation of ROP (Rho GTPases of plants) necessitates a complex and sophisticated regulatory system, in which guanine nucleotide exchange factors (RopGEFs) are key components. It was previously shown that a leucine-rich repeat receptor-like kinase, Arabidopsis pollen receptor kinase 2 (AtPRK2), interacted with RopGEF12 for its membrane recruitment. However, the mechanisms underlying AtPRK2-mediated ROP activation in vivo are yet to be defined. It is reported here that over-expression of AtPRK2 induced tube bulging that was accompanied by the ectopic localization of ROP-GTP and the ectopic distribution of actin microfilaments. Tube depolarization was also induced by a potentially kinase-dead mutant, AtPRK2K366R, suggesting that the over-expression effect of AtPRK2 did not require its kinase activity. By contrast, deletions of non-catalytic domains in AtPRK2, i.e. the juxtamembrane (JM) and carboxy-terminal (CT) domains, abolished its ability to affect tube polarization. Notably, AtPRK2K366R retained the ability to interact with RopGEF12, whereas AtPRK2 truncations of these non-catalytic domains did not. Lastly, it has been shown that the JM and CT domains of AtPRK2 were not only critical for its interaction with RopGEF12 but also critical for its distribution at the plasma membrane. These results thus provide further insight into pollen receptor kinase-mediated ROP activation during pollen tube growth.
authors.affiliation: State Key laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China.
authors.forename: Xin-Ying
authors.initials: XY
authors.lastname: Zhao
authors.forename: Qun
authors.initials: Q
authors.lastname: Wang
authors.forename: Sha
authors.initials: S
authors.lastname: Li
authors.forename: Fu-Rong
authors.initials: FR
authors.lastname: Ge
authors.forename: Liang-Zi
authors.initials: LZ
authors.lastname: Zhou
authors.forename: Sheila
authors.initials: S
authors.lastname: McCormick
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000199:Actins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D009154:Mutation; D030821:Plants, Genetically Modified / Q000235:genetics; D053205:Pollen Tube / Q000254:growth & development* / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; D020662:Guanine Nucleotide Exchange Factors; C525373:RopGEF12 protein, Arabidopsis; C586032:PRK2 protein, Arabidopsis; D011494:Protein Kinases
keywords: Actin microfilaments; CRIB; ROP GTPases.; polar growth; receptor kinase