*Author for correspondence: Email: rgkala@rubberboard.org.in
The natural rubber tree is highly heterozygous hence elite clones are propagated through bud grafting. It is well established that juvenile tissues are more responsive to in vitro propagation techniques. In Hevea also physiological maturity of clonal explants has a direct impact on induction of organogenesis and embryogenesis. The effect is modulated through expression of various genes associated with juvenility including Chlorophyll a/b binding protein gene (Cab gene). The gene was isolated and characterized from Hevea brasiliensis and showed 90% sequence homology to Cab gene from Ricinus communis. In the present study, Cab gene expression with respect to in vitro culture response of leaf explants, harvested from Hevea plants of different maturity was studied. Leaves were harvested from seedlings, somatic plants bud grafted clonal plants and mature trees of clonal origin. A 525 bp Cab gene was differentially expressed in the leaves harvested from these sources. There was markedly more expression of this gene in explants harvested from young seedlings and clonal somatic plants than bud grafted plants and mature field grown trees of clonal origin. Northern analysis also gave similar results. Explants collected from physiologically juvenile sources such as seedlings and clonal somatic plants had higher expression of Cab gene and they also had better in vitro culture response. This indicated that somatic embryogenesis from clonal explants in Hevea resulted in physiological juvenility through clone rejuvenation.
Cab gene, Differential expression RT-PCR, Northern analysis
