The evolving views of the simplest pectic polysaccharides: homogalacturonan.

Pectin is an important component of cell wall polysaccharides and is important for normal plant growth and development. As a major component of pectin in the primary cell wall, homogalacturonan (HG) is a long-chain macromolecular polysaccharide composed of repeated α-1,4-D-GalA sugar units. At the same time, HG is synthesized in the Golgi apparatus in the form of methyl esterification and acetylation. It is then secreted into the plasmodesmata, where it is usually demethylated by pectin methyl esterase (PME) and deacetylated by pectin acetylase (PAE). The synthesis and modification of HG are involved in polysaccharide metabolism in the cell wall, which affects the structure and function of the cell wall and plays an important role in plant growth and development. This paper mainly summarizes the recent research on the biosynthesis, modification and the roles of HG in plant cell wall.