Nuclear Involvement in the Appearance of a Chloroplast-Encoded 32,000 Dalton Thylakoid Membrane Polypeptide Integral to the Photosystem II Complex

Abstract

The genetic locus for the high chlorophyll fluorescent photosystem [PS] II-deficient maize [Zea mays] mutant hcf*-3 was definitively located to the nuclear genome. Fluorography of lamellar polypeptides labeled with [35S]methionine in vivo revealed the specific loss of a heavily labeled 32,000 dalton thylakoid membrane polypeptide as well as its chloroplast encoded precursor species at 34,000 daltons. Examination of freeze-fractured mesophyll and bundle sheath thylakoids from hcf*-3 revealed that both plastid types lacked the large EF particles believed to consist of the PS II reactoin center-core complex and associated light harvesting chlorophyll-proteins. Evidently, synthesis or turnover/integration of the chloroplast-encoded 34,000 to 32,000 dalton polypeptide is under nuclear control and these polypeptides are integral components of PS II which may be required for the assembly or structural stabilization of newly formed PS II reaction centers in mesophyll and bundle sheath chloroplasts.