The Latex of Hevea brasiliensis Contains High Levels of Both Chitinases and Chitinases/Lysozymes

Abstract

The latex of the commercial rubber tree, Hevea brasiliensis, was fractionated by ultracentrifugation as described by G. F. J.Moir ([1959] Nature 184: 1626-1628) into a top layer of rubber particles, a cleared cytoplasm, and a pellet that contains primarily specialized vacuoles known as lutoids. The proteins in each fraction were resolved by two-dimensional gel electrophoresis. Both the pellet fraction and cleared cytoplasm contained large amounts of relatively few proteins, suggesting that laticifers serve a very specialized function in the plant. More than 75% of the total soluble protein in latex was found in the pellet fraction. Twenty-five percent of the protein in the pellet was identified as chitinases/lysozymes, which are capable of degrading the chitin component of fungal cell walls and the peptidoglycan component of bacterial cell walls. Both the chitinase and lysozyme activities were localized exclusively in the pellet or lutoid fraction. The chitinases/lysozymes were resolved into acidic and basic classes of proteins and further purified. An acidic protein (molecular mass 25.5 kD) represented 20% of the chitinase activity in latex; this protein lacked the low level of lysozyme activity that is associated with many plant chitinases. Six basic proteins, having both chitinase and lysozyme activities in various ratios and molecular mass of 27.5 or 26 kD, were resolved. Two of the basic proteins had very high lysozyme specific activities which were comparable to the specific activities reported for animal lysozymes. Like animal lysozymes, but unlike previously characterized plant chitinases/ lysozymes, these basic chitinases/lysozymes were also capable of completely lysing or clearing suspensions of bacterial cell walls. These results suggest that laticifers may serve a defensive role in the plant.Latex is the cytoplasm of highly specialized cells known as laticifers. Most of the volume of the latex from Hevea brasiliensis is filled by rubber particles and specialized vacuoles known as lutoids (5,20). In fact, rubber has been reported to represent from 20 to 60% of the wet weight of latex (5). Laticifers are anastomosed as a result of partial hydrolysis of adjacent walls, and thus form a tube-like network or paracirculatory system through the plant (5). When wound site. This feature oflaticifers is exploited commercially to collect rubber from trees of H. brasiliensis, the sole commercial source of natural rubber.Because laticifers appear to be dedicated primarily to the biosynthesis of the isoprenoid, rubber, it is reasonable to expect the major proteins in latex to be enzymes involved in the biosynthesis of rubber. Indeed, mRNA transcripts encoding enzymes involved in rubber biosynthesis were recently shown to be 20-to 100-fold higher in laticifers than in leaves (1 1). However, transcripts of several putative defense genes including chitinases, pathogenesis-related proteins, phenylalanine ammonia-lyase, chalcone synthase, chalcone isomerase, and 5-enolpyruvylshikimate 3-phosphate synthase wer...

Purification and characterization of extracellular, acidic chitinase isoenzymes from elicitor‐stimulated parsley cells

“…In bean, pea, potato and arabidopsis, several chitinases have been found to possess lysozyme activity (Boller et al, 1983;Mauch et al, 1988a;Verburg and Huynh, 1991;Witte, 1991). In the rubber tree, one acidic chitinase showed no lysozyme activity, whereas six basic isoforms from the same plant exhibited lysozyme activity to varying degrees (Martin, 1991). It is presumed that the coordinate accumulation of chitinases and 1,3-P-glucanases is part of a multicomponent defense response, aimed at degrading the cell walls of many fungi and bacteria.…”

Polyphenoloxidase Silencing Affects Latex Coagulation in Taraxacum Species

“…In addition to a wide range of lowmolecular-weight polypeptides (Nessler and Burnett, 1992;Azarkan et al, 2004), several other proteins and enzymes have been identified in the latices of laticiferous plants. These include the wound-induced proteins trypsin inhibitor, class II chitinase, and glutaminyl cyclase in the latex of papaya (Carica papaya; Azarkan et al, 2004) as well as chitinases and b-1,3-glucanase in the latex of the rubber tree Hevea brasiliensis (Martin, 1991;Subroto et al, 1996). The latex from some plants is a good source of natural rubber, and H. brasiliensis is widely cultivated for this purpose.…”

Valorisation of Proteins from Rubber Tree

“…A previous study showed that most of the hevein from the latex is conserved after isolation from rubber factory effluent, obtaining a concentration of 0.7 g/l and suggesting that the effluent can be a source of proteins with antifungal properties [39]. Other proteins that are identified in the bottom fraction are 1,3-bglucanase and hevamine; the latter shows high chitinase/ lysozyme activity [11,12].…”

“…Protein, being one of the main constituents of biomass and the most valuable part in some cases, can potentially increase the overall economics of rubber plantations. The proteins in rubber tree latex are well-identified [7][8][9][10][11][12][13][14][15], although some are characterised for their allergenic properties [8,9,15]. Less attention is given on proteins in the seeds and the leaves of rubber tree [16,17].…”