谷子叶绿体乙酰辅酶A羧化酶cDNA的克隆和禾本科除草剂靶位点的序列分析

乙酰辅酶A羧化酶是一个生物素羧化酶,它所催化的反应是脂肪酸生物合成中的第一个关键步骤。禾本科植物叶绿体中的乙酰辅酶A羧化酶是两类禾本科除草剂的靶蛋白。从抗除草剂拿捕净和感拿捕净的谷子(Setaria italicaBeauv.)中克隆了两个乙酰辅酶A羧化酶的全长cDNA,分别命名为foxACC-R和foxACC-S,它们推导的蛋白质均编码2 321个氨基酸,然而在第1 780个氨基酸处,foxACC-R编码亮氨酸,而foxACC-S编码异亮氨酸。采用生物信息学方法,我们推断这个cDNA编码的是叶绿体中的乙酰辅酶A羧化酶,并预测了它的功能域和保守区。通过这两个cDNA编码的氨基酸序列与其他乙酰辅酶A羧化酶的序列比较得出结论,亮氨酸/异亮氨酸位点可能是APPs和CHDs两类除草剂作用的关键位点。Southern 杂交分析的结果显示,该基因在谷子基因组中只有一个拷贝。

Cloning of Plastid Acetyl-CoA Carboxylase cDNA from Setaria italica and Sequence Analysis of Graminicide Target Site

Acetyl-CoA carboxylase (ACCase) is a biotinylated enzyme that catalyzes the first committedstep in fatty acid biosynthesis. Graminaceous ACCase in plastid is the target site of two classes ofgraminicide herbicides. Two full-length cDNAs of plastid ACCase from sethoxydim-resistant and sensitiveSetaria italica Beauv., named foxACC-R and foxACC-S, have been cloned. cDNA sequencing showed thatthey encode a protein of 2 321 amino acids long with a pI of 5.89 and a calculated molecular mass of 256kD. The sequences of foxACC-R and foxACC-S have been compared with their homologs from other plantsand analyzed for conserved amino acid regions and their functional domains. It is found that the amino acidat position 1 780 is Leu in foxACC-R other than Ile in foxACC-S and other cereal plastid ACCase. It issuspected that the change of Ile to Leu residue is critical for interaction of plastid ACCase with cerealherbicides APPs and CHDs. According to Southern hybridization, foxACC-R and foxACC-S are bothestimated to be single copy in the genome of S. italica.