The disappearance kinetics of Lhcb polypeptides during dark-induced senescence of leaves

A set of polyclonal antibodies in conjunction with immunoblot technique and integrating densitometry has been used to positively identify and quantify Lhcb 1-6 polypeptides in barley (Hordeum vulgare L.) leaves in which senes cence processes were induced by detachment and dark incubation for 0-6 d. A considerable heterogeneity with regard to disappearance kinetics on a chlo rophyll basis during the course of senescence has been found among individu al Lhcbs. Lhcb 2/1 (the heavier of two polypeptides representing barley Lhc b2) and Lhcb3 exhibited the most rapid disappearance kinetics and decreased to 20 and 42% of their initial levels, respectively, after 6 d of dark inc ubation. Lhcb 1, 4 and 6 levels were maintained through the senescence, at a level very similar to that of fresh leaves, while Lhcb 2/2 (the lighter o f two polypeptides representing barley Lhcb 2) and Lhcb 5 were the most sta ble of all Lhcbs - their relative abundance increased after 6 d of dark inc ubation of the leaves to 181 and 120%, respectively, of the value detected in fresh leaves.