Comparative Proteomics of Primary and Secondary Lutoids Reveals that Chitinase and Glucanase Play a Crucial Combined Role in Rubber Particle Aggregation in Hevea brasiliensis

Abstract

Lutoids are specific vacuole-based organelles within the latex-producing laticifers in rubber tree Hevea brasiliensis. Primary and secondary lutoids are found in the primary and secondary laticifers, respectively. Although both lutoid types perform similar roles in rubber particle aggregation (RPA) and latex coagulation, they vary greatly at the morphological and proteomic levels. To compare the differential proteins and determine the shared proteins of the two lutoid types, a proteomic analysis of lutoid membranes and inclusions was performed, revealing 169 proteins that were functionally classified into 14 families. Biological function analysis revealed that most of the proteins are involved in pathogen defense, chitin catabolism, and proton transport. Comparison of the gene and protein changed patterns and determination of the specific roles of several main lutoid proteins, such as glucanase, hevamine, and hevein, demonstrated that Chitinase and glucanase appeared to play crucial synergistic roles in RPA. Integrative analysis revealed a protein-based metabolic network mediating pH and ion homeostasis, defense response, and RPA in lutoids. From these findings, we developed a modified regulation model for lutoid-mediated RPA that will deepen our understanding of potential mechanisms involved in lutoid-mediated RPA and consequent latex coagulation.

Valorisation of Proteins from Rubber Tree

“…Patatin is currently investigated for food application as emulsifier, gelling agent, and foaming agent [71][72][73][74], and synthesis of monoacylglycerols [75]. Proteomic and genomic studies [76][77][78] might reveal other proteins with potential high-value applications.…”

Ethrel-stimulated prolongation of latex flow in the rubber tree (Hevea brasiliensisMuell. Arg.): an Hev b 7-like protein acts as a universal antagonist of rubber particle aggregating factors from lutoids and C-serum

“…The proteins were identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI TOF MS) as described (12). First, the protein was digested in-gel with bovine trypsin according to a reported method (22).…”

“…The release of the lutoid membrane debris, together with Ca 2+ into the latex cytosolic phase, has been implicated as the initiator of latex coagulation, or the formation of the rubber coagulum (9,11). In vitro analysis shows that proteins in the lutoid, such as hevein, b-1,3-glucanase and the combination of chitinase and b-1,3-glucanase, behave as initiators of rubber particle (RP) aggregation (10,12). In addition, Hevea latex lectin (HLL) on the lutoid membrane has a strong ability to aggregate the RPs (7).…”

“…In summary, under this condition, lutoids are less stable and the duration of latex flow is remarkably prolonged. In addition, ethrel and tapping up-regulate the expression of the gene encoding hevein (16), the initiator of latex coagulation (10,12). Therefore, the prolongation of latex flow in ethrel-stimulated rubber trees may not be related to the enhanced lutoid stability.…”

Highlights on Hevea brasiliensis (pro)hevein proteins

“…To date, 1,499 proteins have been found in latex [12,13]. At least 186 proteins have been reported to be present on rubber particles [14] and 169 have been extracted from lutoids and the bottom fractions [15]. Hevein belongs to the lutoid proteins and represents approximately 20% of the dry matter of the bottom fractions [16,17].…”