Fluctuation of Microfibrillar Protein Level in Lutoids of Primary Laticifers in Relation to the 67 kD Storage Protein in Hevea brasiliensis

Abundant microfibrillar protein inclusions were present in the lutoids of the primary laticifers in Hevea brasiliensis Mull. Arg. Two forms of the inclusions could be distinguished under the electron microscope, each in separate lutoids. As revealed by SDS-PAGE, the 59.5 kD and 63.5 kD proteins were the major components of the microfibrillar protein purified by isoeleettic point precipitation. Western-blotting analysis indicated that they were immunorelated with the 67 kD protein accumulated in the protein-storing cells. The 59.5 kD and 63.5 kD proteins were abundant in the uppermost part, the stem of new shoot and sustained their abundance during the growth and development of new shoot while their contents decreased remarkably in the lower parts of the trunk, accompanying by the accumulation of 3-5 kinds of proteins with low molecular weights. This fluctuating pattern suggested that the degradation of the 59.5 kD and 63.5 kD proteins had nothing to do with the new shoot growth and may be closely related to the primary laticifer differentiation. The 67 kD protein could not be detected in the young stem of new shoot when its leaves were broze-colored while the protein started to be accumulated in the stem, when the leaves of new shoot had matured, behaving like a typical vegetative storage protein.

A Distribution and Ultrastructure of Laticifers in the Phylloclade of <i>Euphorbia caducifolia</i>Haines, a Potential Hydrocarbon Yielding CAM Plant

The present study describes the anatomy, distribution, morphology and ultrastructure of laticifer system in the phylloclades of Euphorbia caducifolia Haines (Family Euphorbiaceae), a potential biofuel yielding, Crassulacean Acid Metabolism (CAM) plant for the first time using light and transmission electron microscopy (TEM). Histochemical tests were performed to identify the principal components of latex using a variety of stains. In cross section, the phylloclade is composed of four distinct regions: the epidermis, cortex, vascular cylinder and pith. The phylloclade anatomy indicated xeromorphic characters and provided an insight about its capacity to grow with very little rainfall and/or inputs on dry or marginal lands. Non-articulated laticifers are present in the cortex, vascular cylinder and pith, but their frequency varies with the tissue type. Highest laticifer frequency was observed in vascular cylinder (9.6%) followed by cortex (3.9%) and pith regions (1.9%). In contrast, laticifer index was found to be higher in the pith (12.7%) followed by cortex (3.8%) and vascular cylinder (2.3%). The discovery of a system of laticifers in E. caducifolia not described earlier could also be of taxonomic value. The histo-chemical tests revealed the presence of lipids, phenols, flavonoids, protein and starch in laticifer. As described by TEM observations laticifers contained distinct cell wall, nucleus and cytoplasm with ribosomes, small and big vacuoles, mitochondria, endoplasmic reticulum, plastids and osmophilic bodies. The lipophilic compounds present in the latex of this species could be used as chemical feedstock for the production of biofuels.

Ethylene and jasmonate as stimulants of latex yield in rubber trees(Hevea brasiliensis):Molecular and physiological mechanisms.A systematic approximation review

The rubber tree Hevea brasiliensis(Willd.Ex Adr.De Juss.)Müell Arg.]is an important source of latex for the production natural rubber.Natural rubber is an important biopolymer used in various industries,but aspects related to hormonal regulation in biosynthesis are still unknown,which would allow optimizing its production.We review the molecular and physiological mechanisms of increases latex regeneration and flow by the stimulation of rubber trees with exogenous applications of ethylene and jasmonate.We found that the increase in latex regeneration by ethylene is due to the increase in gene level expression and enzymatic activity of key photosynthesis and glycolysis enzymes for the generation of precursors in the first phase of rubber biosynthesis.Latex flow is supported by up-regulated genes in sucrose metabolism such as invertases,induction of sucrose transporters(SUT),and aquaporins(PIP)to maintain flow and turgor pressure in laticifers.Meanwhile,the increase in latex yield mediated by jasmonate may be due to the induction of laticifer differentiation in the long term and in the short term be mediated by the induction of small rubber particles(SRPP)as non-enzymatic cofactors in the production of latex.This information contributes to the knowledge of latex biosynthesis,which allows for a greater support for the exogenous application of jasmonates and ethylene to regulate its production.

Localized Effects of Mechanical Wounding and Exogenous Jasmonic Acid on the Induction of Secondary Laticifer Differentiation in Relation to the Distribution of Jasmonic Acid in Hevea brasiliensis

The relationship between the effect of exogenous jasmonic acid (JA) on the induction of secondary laticifer differentiation and the distribution of JA in the seedling of Hevea brasiliensis Mull. Arg. was investigated with the aid of experimental morphological and radioisotope technique. Most radioactivity of H-3-JA sustained in treated site within one hour while no radioactivity was detected in new shoot and the radioactivity in upper leaf was much less than that in the parts below the treated site, suggesting that JA was mainly transported downwards in the shoot of H brasiliensis. Mechanical wounding hindered the entrance of exogenous JA remarkably while held back the entered JA to the regions around wounded site. The effect of exogenous JA and mechanical wounding on the induction of the secondary laticifer differentiation was limited to treated site where high level of JA was expected. Mechanical wounding reduced the effect of exogenous JA on the differentiation of secondary laticifer, which could be ascribed to the hindrance of mechanical wounding to the entrance of exogenous JA. It was concluded from the combined data that a high accumulation of JA was required for inducing the secondary laticifer differentiation in H. brasiliensis.

Plant triterpenoid saponins function as susceptibility factors to promote the pathogenicity of Botrytis cinerea

The gray mold fungus Botrytis cinerea is a necrotrophic pathogen that causes diseases in hundreds of plant species,including high-value crops.Its polyxenous nature and pathogenic success are due to its ability to perceive host signals in its favor.In this study,we found that laticifer cells of Euphorbia lathyris are a source of susceptibility factors required by B.cinerea to cause disease.Consequently,poor-in-latex(pil)mutants,which lack laticifer cells,show full resistance to this pathogen,whereas lot-of-latex mutants,which produce more laticifer cells,are hypersusceptible.These S factors are triterpenoid saponins,which are widely distributed natural products of vast structural diversity.The downregulation of laticifer-specific oxydosqualene cyclase genes,which encode the first committed step enzymes for triterpene and,therefore,saponin biosynthesis,conferred disease resistance to B.cinerea.Likewise,the Medicago truncatula Iha-1 mutant,compromised in triterpenoid saponin biosynthesis,showed enhanced resistance.Interestingly,the application of different purified triterpenoid saponins pharmacologically complemented the diseaseresistant phenotype ofpil and hla-1 mutants and enhanced disease susceptibility in different plant species.We found that triterpenoid saponins function as plant cues that signal transcriptional reprogramming in B.cinerea,leading to a change in its growth habit and infection strategy,culminating in the abundant formation of infection cushions,the multicellular appressoria apparatus dedicated to plant penetration and biomass destruction in B.cinerea.Taken together,these results provide an explanation for how plant triterpenoid saponins function as disease susceptibility factors to promote B.cinerea pathogenicity.

Relationship between the number of tapping-induced secondary laticifer lines and rubber yield among Hevea germplasm

The lack of suitable early selection parameters means that traditional rubber breeding for yield is time consuming and inefficient. Laticifer is a tissue specific fo natural rubber biosynthesis and storage in rubber tree. The number of the secondary laticifers in the trunk bark tissues is positively correlated with rubber yield in the matured rubber trees that are regularly tapped. In the present study the rubber yield from 280 of 4–5 year-old virgin trees from7 cross combinations was compared with the number o newly differentiated secondary laticifers caused by tapping. Results showed that the number of tapping induced lines of secondary laticifers varied in differen germplasm and was positively related to the rubber yield indicating this could be used as a suitable parameter fo early evaluation of yield potential of rubber trees.

The secondary laticifer differentiation in rubber tree is induced by trichostatin A, an inhibitor of histone acetylation

The secondary laticifer, a specific tissue in the secondary phloem of rubber tree, is differentiated from the vascular cambia. The number of the secondary laticifer in the trunk bark of rubber tree is positively correlated with rubber yield. Although jasmonates have been demonstrated to be crucial in the regulation of secondary laticifer differentiation, the mechanism for the jasmonate-induced secondary laticifer differentiation remains to be elucidated.By using an experimental morphological technique, the present study revealed that trichostatin A(TSA), an inhibitor of histone deacetylation, could induce the secondary laticifer differentiation in a concentrationdependent manner. The results suggest that histone acetylation is essential for the secondary laticifer differentiation in rubber tree.