The Maize Transcription Factor KNOTTED1 Directly Regulates the Gibberellin Catabolism Gene ga2ox1
The Maize Transcription Factor KNOTTED1 Directly Regulates the Gibberellin Catabolism Gene ga2ox1
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DOI：
10.1105/tpc.109.068221
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发表时间：
2009-06-01
期刊：
影响因子：
11.6
通讯作者：
Hake, Sarah
中科院分区：
文献类型：
--
作者：
Bolduc, Nathalie;Hake, Sarah
KNOTTED 1（KN 1）-like homeobox（KNOX）转录因子参与植物分生组织的建立和维持，然而，很少有KNOX蛋白的直接靶标被识别。使用双突变体分析和生物化学的组合，我们发现，在玉米（玉米），KN 1负调节赤霉素（GA）的积累通过控制ga 2 ox 1，这编码的酶，使GA失活。GA 2 OX 1 mRNA水平在显性KNOX突变体的未成熟叶片中升高，在无效等位基因kn 1-e1的生殖分生组织中下调。KN 1在体内通过含有两个TGAC基序的顺式调节元件与ga 2 ox 1的内含子结合。VP 16-KN 1在植物中激活含有该结合位点的嵌合启动子的转录。kn 1和ga 2 ox 1 mRNA的表达域在芽顶端分生组织的基部和新启动的叶子的基部重叠，这表明kn 1介导的ga 2 ox 1的激活维持分生组织细胞身份和芽的快速伸长细胞之间的边界。KN 1结合位点在不同禾本科植物的ga 2 ox 1基因中是保守的，这表明通过KNOX蛋白对生物活性GA水平的局部调节是禾本科植物中的一个共同主题。
KNOTTED1 (KN1)-like homeobox (KNOX) transcription factors are involved in the establishment and maintenance of plant meristems; however, few direct targets of KNOX proteins have been recognized. Using a combination of double mutant analysis and biochemistry, we found that in maize (Zea mays), KN1 negatively modulates the accumulation of gibberellin (GA) through the control of ga2ox1, which codes for an enzyme that inactivates GA. The ga2ox1 mRNA level is elevated in immature leaves of dominant KNOX mutants and downregulated in reproductive meristems of the null allele kn1-e1. KN1 binds in vivo to an intron of ga2ox1 through a cis-regulatory element containing two TGAC motifs. VP16-KN1 activates transcription in planta from a chimeric promoter containing this binding site. The domains of expression of kn1 and ga2ox1 mRNAs overlap at the base of the shoot apical meristem and the base of newly initiated leaves, suggesting that KN1-mediated activation of ga2ox1 maintains a boundary between meristem cell identity and rapidly elongating cells of the shoot. The KN1 binding site is conserved in ga2ox1 genes of different grasses, suggesting that the local regulation of bioactive GA levels through KNOX proteins is a common theme in grasses.