Vacuolar-type inorganic pyrophosphatase located on the rubber particle in the latex is an essential enzyme in regulation of the rubber biosynthesis in Hevea brasiliensis

Abstract

V-PPase is found in most plants, some parasitic protists, eubacteria and archaebacteria, and performs crucial functions through the hydrolysis of PPi released from various metabolic pathways. In this study, one V-PPase gene ( Hbvp1) and its promoter were cloned from the rubber tree ( Hevea brasiliensis). The length of Hbvp1 cDNA is 2798 bp and it encodes a protein of 769 amino acids. The Hbvp1 promoter is 1154 bp long, and two JA-responsive regulatory elements, a CGTCA motif and a TGACG motif, are detected in this promoter region. The Hbvp1 protein is a K +-dependent type I V-PPase and the optimum concentration of K + for the maximum Hbvp1 activity is 60 mmol L −1. The expression level of Hbvp1 in the latex and the activity of Hbvp1 on the rubber particle increased markedly with JA stimulation in comparison with the control, indicating that JA could regulate the expression of Hbvp1. Furthermore, Hbvp1 is demonstrated as a rubber particle membrane-associated protein. The efficiency of incorporating [ 14C]isopentenyl pyrophosphate into rubber could be inhibited in vitro by the anti-Hbvp1 antibody. These results suggest that Hbvp1 is a JA-inducible V-PPase located on the rubber particles and might play an important role in regulation of the rubber biosynthesis of H. brasiliensis.