Involved in the phenylpropanoid metabolism by mediating the activation of a number of hydroxycinnamates for the biosynthesis of monolignols and other phenolic secondary metabolites (PubMed:21807887, PubMed:23246835). Catalyzes the formation of CoA esters of cinnamate, 4-coumarate, caffeate and ferulate (PubMed:21807887, PubMed:23246835). Is also able to convert sinapate to its corresponding CoA ester, a reaction that is rarely observed in 4CL catalysis (PubMed:21807887). Is more efficient with substrates in the following order: ferulate > 4-coumarate > sinapate > caffeate > cinnamate (PubMed:21807887). (E)-4-coumarate + ATP + CoA = (E)-4-coumaroyl-CoA + AMP + diphosphate kcat is 1.02 min(-1) with cinnamate as substrate (PubMed:21807887). kcat is 2.88 min(-1) with 4-coumarate as substrate (PubMed:21807887). kcat is 0.84 min(-1) with caffeate as substrate (PubMed:21807887). kcat is 2.04 min(-1) with ferulate as substrate (PubMed:21807887). kcat is 3.18 min(-1) with sinapate as substrate (PubMed:21807887). Phytoalexin biosynthesis; 3,4',5-trihydroxystilbene biosynthesis; 3,4',5-trihydroxystilbene from trans-4-coumarate: step 1/2. Expressed in roots, stems, leaf blades, leaf sheaths and spikelets. Induced by heat stress (PubMed:23994682). Induced by wounding (PubMed:23246835). Down-regulated by UV irradiation (PubMed:23246835). Both substrate-binding domains (SBD1 and SBD2) are involved in the substrate recognition, and are sufficient to confer the substrate specificity. Belongs to the ATP-dependent AMP-binding enzyme family.