Although genetic analysis has identified several proteins required for cellulose synthesis (for review, see Somerville, 2006 , Liepman et al., 2010 ), none of them have definitively been shown to be an essential and integral component of the CSC.
Many of the major advances in the understanding of cellulose biosynthesis in the past decade have been due to the development of fluorescent protein fusions with CESA proteins and the use of fluorescence microscopy to study CSC dynamics in living cells. Expression of a yellow fluorescent protein (YFP)-tagged CESA6 protein was able to complement the cesa6prc1 null mutation, which indicates that YFP–CESA6 integrates into functional CSCs (). YFP–CESA6-labelled CSCs have been visualized as diffraction-limited particles that move within the plane of the plasma membrane at a range of velocities, with an average velocity of around 300 nm min–1 (; ). The displacement of the CSCs is believed to correspond to the synthesis of elementary cellulose fibres by the CSCs. Therefore, several parameters of the behaviour of fluorescent CSCs including the lifetime, velocity, density and organization of plasma membrane-localized CSCs can have implications in the properties of the cellulose microfibrils being synthesized in the plant cell wall. Furthermore, many of these parameters are expected to be influenced by the trafficking of CSCs.
The trafficking of the cellulose synthase complex in ..
The B-complex vitamins fall into the water-soluble group of vitamins and therefore need to be replenished on a daily basis. They are involved in an extremely large number of important metabolic functions in the human body, including energy production, interconversion of substances, detoxification, nerve transmission, blood formation, synthesis of proteins and fats, the production of steroid hormones, the maintenance of blood sugar levels and appetite, the toning of muscles, etc.
Vitamins B1, B2, and B6 do not function properly in the body until they are made into their coenzyme forms by the addition of phosphate. Because this process does not always occur efficiently, includes the coenzyme forms of these B vitamins.
How is the CesA position in cellulose synthesis complex?
A distinctive feature of the cells of higher plants is the cell wall, an extracellular assembly that acts like an external skeleton. Among other things, it allows the cell to support a sizeable internal osmotic pressure, a prerequisite for withstanding the pull of gravity. The cell wall derives its robust mechanical properties from its ingenious construction: it consists of stacks of thin lamellae (), all deposited parallel to the plasma membrane, that are formed by long parallel almost purely crystalline cellulose microfibrils (CMFs) embedded in a matrix of polysaccharide “packing” material (,). Its ubiquitous presence within plant cell walls makes cellulose the most abundant polymeric material in the biosphere. Despite its vital importance both in plant cell function and as a raw material, the primary event of the biosynthesis of cellulose is still only partially understood.
Trafficking of the Plant Cellulose Synthase Complex | …
Although the idea that the CSC moves was widely accepted, the question of the origin of this movement has so far received less attention. Obvious candidates for the required force production are motor proteins, molecular chemical energy transducers that are involved in many different biological tasks (,). Examples are processive molecular motors such as kinesin, which can transport organelles and vesicles using cytoskeletal elements as tracks, or nonprocessive motors such as myosins that deliver the power strokes for muscle contraction, both using ATP as fuel. Indeed, one of the early theories () assumed the CSC to be linked by a motor protein to a cortical microtubule, which then acted as a rail to guide the motion. Another proposal () had the cortical microtubules act as force producers themselves, which by setting up a shear flow in the membrane, provide a motive force to the CSC. Later, it was realized that in principle the energy released by the glucose polymerization process could by itself be sufficient to propel the CSC (). In addition, it was shown that preventing the proper crystallization of the CMF by treatment of cells with the drug Calcofluor led to a thickening of the cell wall, suggesting a dysfunctional dispersion of the CSC along the membrane (). This observation clearly correlates the movement of the CSC with the polymerization and crystallization processes of the CMFs. To date, however, a detailed mechanistic explanation of how the motion of the CSC is achieved was lacking.