Subcellular localization and interactions among rubber particle proteins from Hevea brasiliensis.

Daniel Brown,Alessandra Di Cola,Chiara Lonoce,Mathin Ahmadi,Lorenzo Frigerio,Mistianne Feeney,Roslinda Sajari

doi:10.1093/jxb/erx331

Abstract

Natural rubber (polyisoprene) from the rubber tree Hevea brasiliensis is synthesized by specialized cells called laticifers. It is not clear how rubber particles arise, although one hypothesis is that they derive from the endoplasmic reticulum (ER) membrane. Here we cloned the genes encoding four key proteins found in association with rubber particles and studied their intracellular localization by transient expression in Nicotiana benthamiana leaves. We show that, while the cis-prenyltransferase (CPT), responsible for the synthesis of long polyisoprene chains, is a soluble, cytosolic protein, other rubber particle proteins such as rubber elongation factor (REF), small rubber particle protein (SRPP) and Hevea rubber transferase 1-REF bridging protein (HRBP) are associated with the endoplasmic reticulum (ER). We also show that SRPP can recruit CPT to the ER and that interaction of CPT with HRBP leads to both proteins relocating to the plasma membrane. We discuss these results in the context of the biogenesis of rubber particles.

Highlights

Natural rubber (NR) is a globally essential, industrial raw material used in the manufacture of a vast array of products, ranging from aircraft and vehicle tyres to medical apparel and devices
The most abundant proteins found to be involved in rubber biosynthesis are isopentenylpyrophosphate (IPP) polymerizing enzyme, cis-prenyltransferase (CPT); rubber elongation factor (REF) and small rubber particle protein (SRPP) (Light et al, 1989; Oh et al, 1999; Asawatreratanakul et al, 2003)
In order to test this hypothesis, we have investigated the subcellular localization and the patterns of interaction of all the factors that are known to be involved in rubber biosynthesis and associated to rubber particles (RPs), by transient expression in Nicotiana benthamiana leaves

Summary

Introduction

Natural rubber (NR) is a globally essential, industrial raw material used in the manufacture of a vast array of products, ranging from aircraft and vehicle tyres to medical apparel and devices. While CPT6 is a cytosolic protein, SRPP, REF and HRBP localize to the ER. When we co-expressed CPT6-YFP with REF-mCherry, the fluorescence signals did not co-localize, with CPT6YFP remaining cytosolic/nucleoplamic and REF-mCherry remaining ER associated (see Supplementary Fig. S2G–I).

Results

Conclusion