Structure, organization, and functions of cellulose synthase complexes in higher plants

Annually, plants produce about 180 billion tons of cellulose making it the largest reservoir of organic carbon on Earth. Cellulose is a linear homopolymer of β(1-4)-linked glucose residues. The coordinated synthesis of glucose chains is orchestrated by specific plasma membrane-bound cellulose synthase complexes (CelS). The CelS is postulated to be composed of approximately 36 cellulose synthase (CESA) subunits. The CelS synthesizes 36 glucose chains in close proximity before they are further organized into microfibrils that are further associated with other cell wall polymers. The 36 glucose chains in a microfibril are stabilized by intraand inter-hydrogen bonding which confer great stability on microfibrils. Several elementary microfibrils come together to form macrofibrils. Many CESA isoforms appear to be involved in the cellulose biosynthetic process and at least three types of CESA isoforms appear to be necessary for the functional organization of CelS in higher plants.