Modified RING finger, HC subclass (C4C4-type), found in Arabidopsis thaliana cellulose synthase A (CesA) catalytic subunit 1-10, and similar proteins from plant
The family includes a group of plant catalytic subunits of cellulose synthase terminal complexes ("rosettes") required for beta-1,4-glucan microfibril crystallization, a major mechanism of the cell wall formation. CesA1, also known as protein RADIALLY SWOLLEN 1 (RSW1), is required during embryogenesis for cell elongation, orientation of cell expansion and complex cell wall formations, such as interdigitated pattern of epidermal pavement cells, stomatal guard cells, and trichomes. It plays a role in lateral roots formation, but seems unnecessary for the development of tip-growing cells such as root hairs. CesA2, also known as Ath-A, is involved in the primary cell wall formation. It forms a homodimer. CesA3, also known as constitutive expression of VSP1 protein 1, or isoxaben-resistant protein 1, or Ath-B, or protein ECTOPIC LIGNIN 1, or protein RADIALLY SWOLLEN 5 (RSW5), is involved in the primary cell wall formation, especially in roots. CesA4, also known as protein IRREGULAR XYLEM 5 (IRX5), is involved in the secondary cell wall formation, and required for the xylem cell wall thickening. CesA5 may be partially redundant with CesA6. CesA6, also known as AraxCelA, isoxaben-resistant protein 2, protein PROCUSTE 1, or protein QUILL, is involved in the primary cell wall formation. Like CesA1, CesA6 is critical for cell expansion. The CESA6-dependent cell elongation seems to be independent of gibberellic acid, auxin, and ethylene. CesA6 interacts with and moves along cortical microtubules for the process of cellulose deposition. CesA7, also known as protein FRAGILE FIBER 5, or protein IRREGULAR XYLEM 3 (IRX3) is involved in the secondary cell wall formation and required for the xylem cell wall thickening. CesA8, also known as protein IRREGULAR XYLEM 1 (IRX1) or protein LEAF WILTING 2, is involved in the secondary cell wall formation and required for the xylem cell wall thickening. The biological function of CesA9 and CesA10 remain unclear. CesA1, CesA3, and CesA6 form a functional complex essential for primary cell wall cellulose synthesis, while CesA4, CesA7, and CesA8 form a functional complex located in secondary cell wall deposition sites. All family members contain an N-terminal C4C4-type RING-HC finger and a C-terminal glycosyltransferase family A (GT-A) domain.