Cloning of <italic>Ta4CL1 </italic>and its function in promoting plant growth and lignin deposition in transgenic <italic>Arabidopsis</italic> plants

Abstract

<p id="C3">4-Coumarate:coenzyme A ligase (4CL; EC 6.2.1.12) acts upstream of the branch point of phenylpropanoid, which is a key enzyme in the phenylpropanoid metabolic pathways for monolignol and flavonoid biosynthesis, and these compounds play important roles in plant growth and development as well as stress adaptability. Many 4CLs had been extensively studied in dicotyledons, but their function in monocotyledons, especially in crops, was relatively poorly understood. In this study, <italic>Ta4CL1, </italic>which encoded 4-Coumarate:coenzyme A ligase, was isolated from common wheat by RACE technique. Polygenetic analysis revealed that Ta4CL1 could be clustered to the same group of 4CLs from rice, maize, and sorghum, which was mainly involved in lignin biosynthesis. <italic>Ta4CL1-</italic>overexpressed <italic>Arabidopsis</italic> lines, <italic>at4cl1</italic>, <italic>at4cl3</italic>, and <italic>at4cl14cl3</italic> as well as their corresponding functional recovery lines were used to elucidate the function of<italic> Ta4CL1 </italic>in the phenylpropanoid metabolic pathway. The results suggested that Ta4CL1 had similar function with At4CL1 in regulating lignin biosynthesis but it had no effect on flavonoid biosynthesis. Ta4CL was the major contributor of 4CL enzyme activity in transgenic <italic>Arabidopsis</italic> plants. Overexpression of <italic>Ta4CL</italic> led to enlarged leaves and thickened stems in transgenic <italic>Arabidopsis</italic> seedlings, the expression of <italic>Ta4CL </italic>was also affected by MeJA, GA, and IAA treatments. These results provide the theoretical basis for improving the utilizing efficiency of plant straws using <italic>Ta4CL1 </italic>by genetic engineering.