The biology of arabinogalactan proteins in plant abiotic stress and reproduction

Cell wall modifications are integral to many plant developmental processes and involved in plant tolerance to environmental stress. The arabinogalactan proteins (AGPs) are a highly diverse class of heavily glycosylated proteins, included in the broad family of cell wall hydroxyproline-rich glycoproteins. This diverse family of cell wall glycoproteins is widely distributed in the plant kingdom where they play fundamental roles in growth and development processes. AGPs have been suggested to intervene during stress tolerance where a transcriptional reprogramming induces the production of a specific group of cell wall proteins, among which are the AGPs, affecting the synthesis, deposition, and reorganisation of cell wall polysaccharides and subsequently cell wall architecture, conditioning plant cell responses. In this review, we present an overview of the accumulated knowledge on AGP biosynthesis and function, giving particular emphasis to their involvement in abiotic stress tolerance and plant reproduction as these two physiological processes are essential for plant growth and seed yield. Understanding the role of AGPs during these conditions contributes for a better understanding of AGP biology and ultimately to integrate it in new biotechnology methodologies to improve plant crop production.