Arabidopsis auxin response factor6 and 8 regulate jasmonic acid biosynthesis and floral organ development via repression of class 1 KNOX genes.
Two mutations in Arabidopsis thaliana, auxin response factor6 (arf6) and arf8, concomitantly delayed the elongation of floral organs and subsequently delayed the opening of flower buds. This phenotype is shared with the jasmonic acid (JA)-deficient mutant dad1, and, indeed, the JA level of arf6 arf8 flower buds was decreased. Among JA biosynthetic genes, the expression level of DAD1 (DEFECTIVE IN ANTHER DEHISCENCE1) was markedly decreased in the double mutant, suggesting that ARF6 and ARF8 are required for activation of DAD1 expression. The double mutant arf6 arf8 also showed other developmental defects in flowers, such as aberrant vascular patterning and lack of epidermal cell differentiation in petals. We found that class 1 KNOX genes were expressed ectopically in the developing floral organs of arf6 arf8, and mutations in any of the class 1 KNOX genes (knat2, knat6, bp and hemizygous stm) partially suppressed the defects in the double mutant. Furthermore, ectopic expression of the STM gene caused a phenotype similar to that of arf6 arf8, including the down-regulation of DAD1 expression. These results suggested that most defects in arf6 arf8 are attributable to abnormal expression of class 1 KNOX genes. The expression of AS1 and AS2 was not affected in arf6 arf8 flowers, and as1 and arf6 arf8 additively increased the expression of class 1 KNOX genes. We concluded that ARF6 and ARF8, in parallel with AS1 and AS2, repress the class 1 KNOX genes in developing floral organs to allow progression of the development of these organs.
Tabata
Ryo
R
Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
Ikezaki
Masaya
M
Fujibe
Takahiro
T
Aida
Mitsuhiro
M
Tian
Chang-en
CE
Ueno
Yoshihisa
Y
Yamamoto
Kotaro T
KT
Machida
Yasunori
Y
Nakamura
Kenzo
K
Ishiguro
Sumie
S
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D019521:Body Patterning / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D003517:Cyclopentanes / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D035264:Flowers / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D054883:Oxylipins / Q000378:metabolism*; D010641:Phenotype; D054466:Phospholipases A1 / Q000235:genetics / Q000378:metabolism; D019441:Plant Epidermis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
C463739:AS2 protein, Arabidopsis; C456239:ASYMMETRIC LEAVES1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003517:Cyclopentanes; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C092213:KNAT2 protein, Arabidopsis; C491111:KNAT6 protein, Arabidopsis; D054883:Oxylipins; D012097:Repressor Proteins; C097496:STM protein, Arabidopsis; D014157:Transcription Factors; C517136:auxin response factor 6, Arabidopsis; C495666:auxin response factor 8, Arabidopsis; C011006:jasmonic acid; C445094:DAD1 protein, Arabidopsis; D054466:Phospholipases A1