Comparative Proteomics of Rubber Latex Revealed Multiple Protein Species of REF/SRPP Family Respond Diversely to Ethylene Stimulation among Different Rubber Tree Clones.pdf
Natural rubber, produced commercially from Hevea brasiliensis trees, has unique 19 properties and many applications cannot use synthetic rubber as a substitute. Rubber elongation 20 factor (REF) and small rubber particle protein (SRPP) are two key factors for natural rubber 21 biosynthesis. Much remains to be understood about the roles of these proteins in rubber formation. 22 Six genes from the REF/SRPP families, REF138,175,258 and SRPP117,204,243, were characterized from Hevea 23 brasiliensis RY 7-33-97. The encoded proteins contain a shared REF domain, however, the REFs have 24 a variable and long N-terminal, whereas SRPPs have a variable and long C-terminal. REF258, an 25 unusual REF, has a β subunit of ATPase in its N-terminal. Each REF/SRPP protein separates into 26 multiple protein spots on 2-DE gels, indicating each REF/SRPP has several different protein forms 27 (isoforms). In general, the total abundance of each REF/SRPP protein decreased or changed little 28 upon ethylene stimulation, whereas the abundance of multiple isoforms of each REF/SRPP protein 29 changed differently following ethylene stimulation, with some increasing but others decreasing. 30 Among the three rubber tree clones with different levels of latex productivity, total abundance of 31 each REF/SRPP was similar, but the abundance of specific isoforms of each REF/SRPP differed 32 significantly. REF175 and REF258 each have two isoforms dominate and ethylene-responsive in the 33 high latex productivity clone RY 8-79, and insignificant in relatively low latex productivity clone PR 34 107. These results indicate that multiple isoforms of each REF/SRPP protein behave diversely in 35 different rubber tree clones and respond diversely to ethylene stimulation. REF175 and REF258 each 36 have two isoforms showed positive relations to latex production in the rubber tree.