Dynamic function and regulation of apoplast in the plant body

Abstract

Apoplast is the internal environment of plant. Our body posses the intemal environment that consists of blood, lympha, and tissue fluid. Plant cells are also cultivated and surrounded by a liquid medium in the apoplast. As well as various important functions of the internal environment in our body, apoplast function is also prerequisite for the plant life. There are so far seven distinct functions of apoplast.(1) Growth regulation with apoplastic enzymes by altering cell-wall properties through degradation, synthesis, orientation and cross-linking of supra molecules of cell walls, such as cellulose, non-cellulosic polysaccharides, proteins, and lignin; (2) Skeleton sustained by cellulose microfibrils, lignin and various types of structural proteins with distinctively high content of hydroxyproline, proline or glycine; (3) Skin to defend symplast from desiccation, pathogens' attack and harmful environmental factors, such as ozone and sulfur dioxide; (4) Transportation route for not only well-known molecules of water, inorganic ions, and sugar, but also plant hormones, oligosaccharides and proteins; (5) Homeostasis of the internal environment by controlling ionic balance, pH and water content; (6) Adhesion of cell to cell; (7) Gas exchange space of leaf for photosynthesis. The present article reviews the recent 'advances in studies of several aspects of the dynamic function and regulation of apoplast.

Effect of Manganese Toxicity on the Proteome of the Leaf Apoplast in Cowpea

“…The leaf apoplast is a compartment of storage and physiological reactions like intercellular signaling, defense against biotic and abiotic stresses, and transport of water and nutrients (Sakurai, 1998;Sattelmacher, 2001). The extracellular space of plants contains acidic (anionic) and basic (cationic) POD isoenzymes present both as cell wall-bound and soluble enzymes with differential affinities to substrates (Campa, 1991;Kärkö nen et al, 2002).…”

Comparative Analyses of Extracellular Matrix Proteome: An Under-Explored Area in Plant Research

“…In osmotic, salinity and dehydration stress, the expansion ability of the cell wall decreases. Correlated with this weakening was a substantial decrease in the proportion of crystalline cellulose in the primary cell wall while the amount of insoluble proteins (such as HRGPs) associated with the wall was increased relative to other wall components (Sakurai et al, 1998).…”

“…In addition to the crucial role of CWPs in growth and development, these proteins or peptides are also involved in plant defence mechanisms in response to pathostress. Earlier, a number of ECM proteins have been shown to play a crucial role in plant defence against microbes (Sakurai, 1998), including pathogenesis-related (PR) proteins, chitinases and endo-b-1,3-glucanases, that are known to directly interact with pathogens (Jung et al, 2004;Jones et al, 2006). However, plants also deploy a repertoire of proteins in the wall that act as a surveillance system to allow the early detection of an impending pathogen assault.…”

Significance of Unusual Features of the Anthers of Spathoglottis plicata Bl.

“…Therefore, it is cogent to assume that thick cell walls of meiocytes not only substitute for callose to maintain cell to cell contact but also prevent their cohesion and fusion. Since cell walls also constitute apoplast (Sakurai 1998), they presumably protect the symplast from dehydration and determine the microspore polarity. Presence of thin cell walls and absence of storage carbohydrates are characteristic features of all meristematic and secretory tissues including meiocytes and tapetum.…”

“…In many male sterile plants pollen sterility is linked with the absence or poor synthesis of anther callose or failure of its degradation (Homer Jr. 1977, Theis and Robbelen 1990, Hegde and Isaacs 1992. According to Sakurai (1998) callose functions as an apoplastic molecule. So far 6 facets of anther callose functions are envisaged: (i) adhesion of meiocyte to meiocyte without allowing their fusion and cohesion (ElGhazaly and Jensen 1987, Theis and Robbelen 1990, Bedinger 1992, (ii) skin to defend symplast from dehydration (Barskaya andBalina 1971, Vijayaraghavan andShukla 1977), (iii) skeleton to establish microspore polarity (Blackmore and Barnes 1988), (v) growth regulation by directing the orientation of cellulosic microfibrils (van Amstel and Kengen 1996), (v) transportation route for selective nutrients by virtue of its ability to function as a 'selective molecular filter ' (Heslop-Harrison and Mackenzie 1967, Knox and Heslop-Harrison 1970, Southworth 1971, and (vi) template or mold for exine wall formation (Vijayaraghavan and Shukla 1977 grains.…”