title: MCA1 and MCA2 that mediate Ca2+ uptake have distinct and overlapping roles in Arabidopsis.
abstract: Ca(2+) is important for plant growth and development as a nutrient and a second messenger. However, the molecular nature and roles of Ca(2+)-permeable channels or transporters involved in Ca(2+) uptake in roots are largely unknown. We recently identified a candidate for the Ca(2+)-permeable mechanosensitive channel in Arabidopsis (Arabidopsis thaliana), named MCA1. Here, we investigated the only paralog of MCA1 in Arabidopsis, MCA2. cDNA of MCA2 complemented a Ca(2+) uptake deficiency in yeast cells lacking a Ca(2+) channel composed of Mid1 and Cch1. Reverse transcription polymerase chain reaction analysis indicated that MCA2 was expressed in leaves, flowers, roots, siliques, and stems, and histochemical observation showed that an MCA2 promoter::GUS fusion reporter gene was universally expressed in 10-d-old seedlings with some exceptions: it was relatively highly expressed in vascular tissues and undetectable in the cap and the elongation zone of the primary root. mca2-null plants were normal in growth and morphology. In addition, the primary root of mca2-null seedlings was able to normally sense the hardness of agar medium, unlike that of mca1-null or mca1-null mca2-null seedlings, as revealed by the two-phase agar method. Ca(2+) uptake activity was lower in the roots of mca2-null plants than those of wild-type plants. Finally, growth of mca1-null mca2-null plants was more retarded at a high concentration of Mg(2+) added to medium compared with that of mca1-null and mca2-null single mutants and wild-type plants. These results suggest that the MCA2 protein has a distinct role in Ca(2+) uptake in roots and an overlapping role with MCA1 in plant growth.
authors.affiliation: Department of Biology, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Yamanaka
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: Kendo
authors.initials: K
authors.lastname: Mori
authors.forename: Masataka
authors.initials: M
authors.lastname: Nakano
authors.forename: Tomomi
authors.initials: T
authors.lastname: Imamura
authors.forename: Hajime
authors.initials: H
authors.lastname: Kataoka
authors.forename: Asuka
authors.initials: A
authors.lastname: Terashima
authors.forename: Kazuko
authors.initials: K
authors.lastname: Iida
authors.forename: Itaru
authors.initials: I
authors.lastname: Kojima
authors.forename: Takeshi
authors.initials: T
authors.lastname: Katagiri
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Iida
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D005816:Genetic Complementation Test; D008274:Magnesium / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D009154:Mutation; D018517:Plant Roots / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics; D012441:Saccharomyces cerevisiae
chemical_list: D029681:Arabidopsis Proteins; D015220:Calcium Channels; D004269:DNA, Bacterial; C520286:MCA1 protein, Arabidopsis; D008565:Membrane Proteins; D018749:RNA, Plant; C036483:T-DNA; D008274:Magnesium; D002118:Calcium