Necessary for the introduction of cis unsaturation into fatty acids. Catalyzes the dehydration of (3R)-3-hydroxydecanoyl-ACP to E-(2)-decenoyl-ACP and then its isomerization to Z-(3)-decenoyl-ACP. Can catalyze the dehydratase reaction for beta-hydroxyacyl-ACPs with saturated chain lengths up to 16:0, being most active on intermediate chain length