Detection of an In Vivo 8 kD C-terminal Breakdown Product of D1-protein under Visible and UV-B Light

An 8 kD in vivo turnover product of D1 polypeptide was identified using a C-terminal specific anti-D1-antibody in thylakoids isolated from 5–10 days old seedlings of wheat (Triticum aestivum cv HD2329). Eight days old wheat seedlings grown under visible light were irradiated with UV-B (1 mW cm⁻²) alone (0-5h) and Tricine SDS-PAGE was run of the isolated thylakoids. UV-B exposure of intact wheat leaves generates a fragment of 24 kD and concomitant increase in 8 kD fragment was also observed. From these results it is concluded that in wheat visible light induces the breakdown of D1 polypeptide into an 8 kD C-terminal thylakoid bound fragment and UV-B stress results in an increase in 8 kD breakdown fragment, thus suggesting that visible light/UV-B has a common hot spot on D1 protein in wheat.