Insect gall induction and phytohormones

Abstract

It has recently become clear that a wide range of insects contains phytohormones such as cytokinin, auxin, and abscisic acid. Gall induction by insects has attracted attention as a phenomenon that may involve phytohormones synthesized by the insects themselves. Since the induction of insect galls is accompanied by extensive cell proliferation and vascular bundle formation, and the gall tissue exhibits high sink function, the involvement of auxin and cytokinin has long been postulated. In this review, we will summarize information on insect phytohormones, including their distribution, biosynthesis, and localization, which is necessary to consider their physiological functions in insect gall induction. Additionally, we will discuss the gaps in knowledge that need to be addressed to further understand their importance.