Biosynthesis, physiology, and functions of hydroxycinnamic acid amides in plants

The study of hydroxycinnamic acid amides (HCAAs) which are a group of secondary metabolites has been an interesting one and has become one of the important researches at present. Accumulation of several plant amides was detected in various plants, which play important role in plant growth and development. This paper aims to review the biosynthesis, physiology, and functions of HCAA accumulation in plants during plant growth and development as well as in response to senescence and drought stress. HCAAs are secondary metabolites derived from phenylalanine and tyrosine pathway. Phenylalanine ammonia lyase (PAL) and 4-coumarate CoA ligase (4CL) hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl) transferase (THT) and tyrosine decarboxylase (TyDC) are essential enzymes for HCAA biosynthesis. HCAAs contribute to many developmental processes as well as plant responses against biotic and abiotic stress responses. However, there is a need to specifically investigate the role of many HCAAs in view of plant molecular biology since it is still not fully conceptualized and explained at present.