Ribosomal and polyadenylated RNA content of rubber tree latex, association with sucrose level and latex pH

Abstract

Poly(A) content of latex polysomes in tapped Hevea trees of different age and clonal origin varied from 0.1 μg to 0.5 μg ml −1 latex cytosol indicating poly(A) +RNA levels of 1.5 μg – 7.5 μg ml −1 and between 3% and 7.5% in proportion to rRNA. The level of rRNA was in the range 43 μg – 120 μg ml −1. The poly(A) +RNA exhibited a polydisperse sedimentation pattern with prominent peaks at 16 S, 20 S and 24 S, and an apparent mean size of 2270 nucleotides. Clonal differences in rRNA were significant and within different clonal trials were associated with variations in the level of latex sucrose and in latex pH suggesting an association with the activity of latex glycolysis. Level of polysomal poly(A), also in proportion to rRNA, was significantly higher in clone PB 217 than in clones GT 1 and PB 235 exhibiting much lower sucrose content of latex. Bark treatment with ethephon increasing latex pH, sucrose utilization and latex yield increased the levels of rRNA and particularly of poly(A) +RNA. This increase did not result in an increase of soluble proteins and may thus be concerned with synthesis of proteins bound to latex structures. Low levels of polysomes for cytoplasmic structure formation may be involved in association of low sucrose with latex vessel senescence.