Mitochondrial/cytosolic acetyl CoA and rubber biosynthesis genes expression in Hevea brasiliensis latex and rubber yield

Abstract

Expressions of the 22 genes involved in rubber biosynthesis, from the acetyl CoA genesis and the mevalonate (MVA) pathway to IPP polymerization, were analyzed by real-time polymerase chain reaction (PCR). The results revealed that the expressions of most genes were not related to the latex yield trait when compared among three high- and three low-yielding rubber clones. Only the genes HMGR3 and SRPP1 were significantly up-regulated in low-yielding clones. The higher expression of the SRPP1 gene in low-yielding clones suggested a possible increase in the number and higher rubber biosynthetic activity of the active small rubber particles, which may produce latex with higher viscosity, impairing the latex flow and limiting the latex yield. The up-regulation of the HMGR3 gene in low-yielding clones may reflect a higher amount or activity or both of Frey-Wyssling particles (plastids) in their latex. These plastids have been shown to be involved in oxidative processes that induced earlier laticifers plugging, which also impaired the latex flow and yield. In conclusion, a possible crossover between the cytosolic M VA and the plastidic 1-deoxy-D-xylulose-5-phosphate/2-C-methyl-D-erythritol-4-phosphate (DXP/ MEP) pathways is suggested, which might especially take place in the laticifers of the high-yielding clones, to fulfill the requirement in isopentenyl pyrophosphate for more active rubber biosynthesis.