title: Expression of class I knotted1-like homeobox genes in the storage roots of sweetpotato (Ipomoea batatas).
abstract: As a first step in clarifying the involvement of class I knotted1-like homeobox (KNOXI) genes in the storage root development of sweetpotato (Ipomoea batatas), we isolated three KNOXI genes, named Ibkn1, Ibkn2 and Ibkn3, expressed in the storage roots. Phylogenetic analysis showed that Ibkn1 was homologous to the SHOOT MERISTEMLESS (STM) gene of Arabidopsis, while Ibkn2 and Ibkn3 were homologous to the BREVIPEDICELLUS (BP) gene. Of these, expression of Ibkn1 and Ibkn2 were upregulated in developing and mature storage roots compared with fibrous roots. Ibkn1 and Ibkn2 showed different expression patterns in the storage roots. Ibkn1 was preferentially expressed at the proximal end and around the primary vascular cambium, while Ibkn2 expression was highest in the thickest part and lower in both the proximal and distal ends. In contrast to Ibkn1 and Ibkn2, expression of Ibkn3 in roots was not consistent among sweetpotato cultivars. The distribution of endogenous trans-zeatin riboside (t-ZR) in sweetpotato roots showed a similarity to the expression pattern of KNOXI genes, supporting the idea that KNOXI genes control cytokinin levels in the storage roots. The physiological functions of these KNOXI genes in storage root development are discussed.
authors.affiliation: Crop Functionality and Utilization Research Team, National Agricultural Research Center for Kyushu Okinawa Region, Miyakonojo, Miyazaki, Japan. mtanaka@affrc.go.jp
authors.forename: Masaru
authors.initials: M
authors.lastname: Tanaka
authors.forename: Nakao
authors.initials: N
authors.lastname: Kato
authors.forename: Hiroki
authors.initials: H
authors.lastname: Nakayama
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakatani
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takahata
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D003583:Cytokinins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D027723:Ipomoea batatas / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D007541:Isopentenyladenosine / Q000031:analogs & derivatives / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D003583:Cytokinins; D018398:Homeodomain Proteins; C405985:Knox1 protein, plant; D010940:Plant Proteins; D007541:Isopentenyladenosine; C009699:zeatin riboside