The BLADE-ON-PETIOLE 1 gene controls leaf pattern formation through the modulation of meristematic activity in Arabidopsis.
The plant leaf provides an ideal system to study the mechanisms of organ formation and morphogenesis. The key factors that control leaf morphogenesis include the timing, location and extent of meristematic activity during cell division and differentiation. We identified an Arabidopsis mutant in which the regulation of meristematic activities in leaves was aberrant. The recessive mutant allele blade-on-petiole1-1 (bop1-1) produced ectopic, lobed blades along the adaxial side of petioles of the cotyledon and rosette leaves. The ectopic organ, which has some of the characteristics of rosette leaf blades with formation of trichomes in a dorsoventrally dependent manner, was generated by prolonged and clustered cell division in the mutant petioles. Ectopic, lobed blades were also formed on the proximal part of cauline leaves that lacked a petiole. Thus, BOP1 regulates the meristematic activity of leaf cells in a proximodistally dependent manner. Manifestation of the phenotypes in the mutant leaves was dependent on the leaf position. Thus, BOP1 controls leaf morphogenesis through control of the ectopic meristematic activity but within the context of the leaf proximodistality, dorsoventrality and heteroblasty. BOP1 appears to regulate meristematic activity in organs other than leaves, since the mutation also causes some ectopic outgrowths on stem surfaces and at the base of floral organs. Three class I knox genes, i.e., KNAT1, KNAT2 and KNAT6, were expressed aberrantly in the leaves of the bop1-1 mutant. Furthermore, the bop1-1 mutation showed some synergistic effect in double mutants with as1-1 or as2-2 mutation that is known to be defective in the regulation of meristematic activity and class I knox gene expression in leaves. The bop1-1 mutation also showed a synergistic effect with the stm-1 mutation, a strong mutant allele of a class I knox gene, STM. We, thus, suggest that BOP1 promotes or maintains a developmentally determinate state in leaf cells through the regulation of class I knox genes.
Ha
Chan Man
CM
Division of Molecular Life Science, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang, Kyungbuk, 790-784, Korea.
Kim
Gyung-Tae
GT
Kim
Byung Chul
BC
Jun
Ji Hyung
JH
Soh
Moon Soo
MS
Ueno
Yoshihisa
Y
Machida
Yasunori
Y
Tsukaya
Hirokazu
H
Nam
Hong Gil
HG
D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D019521:Body Patterning / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D035264:Flowers / Q000033:anatomy & histology; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000502:physiology*; D008854:Microscopy, Electron; D009154:Mutation; D018515:Plant Leaves / Q000033:anatomy & histology / Q000254:growth & development*; D018547:Plant Stems / Q000033:anatomy & histology
D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C092212:KNAT1 protein, Arabidopsis; C092213:KNAT2 protein, Arabidopsis; C097496:STM protein, Arabidopsis