REGULATION OF CHLOROPLAST GENE-EXPRESSION IN ISOLATED COTYLEDONS OF YELLOW LUPINE BY PHYTOHORMONES, LIGHT, AND TEMPERATURE

A model system has been optimized for study of cytokinin and ABA regul ation of the expression of chloroplast protein genes in isolated cotyl edons of yellow lupine (Lupinus luteus L.). Preincubation of cotyledon s on a solution of BAP (2.2.10(-5) M) in the dark for a period of 12 h activates differentiation of etioplasts and increases chlorophyll con tent three- to fourfold during 8-10 h of subsequent illumination. ABA blocks this process. Differential regulation is demonstrated for accum ulation of chloroplast gene transcripts during germination of lupine s eeds in the dark. Transcripts of the first group of genes (psbB, psbE, petA, atpA) are detected in dry seeds, their content increasing gradu ally in the course of germination. Transcripts of the second group of genes (psbA, psbD, rbcL) appear in cotyledons during the period betwee n 24 and 48 h of germination of lupine seeds. It is demonstrated by We stern blotting analysis that BAP induces synthesis of the apoprotein o f cytochrome b559 in cotyledons in the dark. Synersism is detected in the action of BAP and light on accumulation of this protein. Abscisic acid inhibits its appearance under light. Number of transcripts of the psbA gene is little altered by BAP and ABA under conditions of normal temperature. At 40-degrees-C BAP promotes, but ABA inhibits accumulat ion of mRNA of the psbA gene. At a temperature of 46-degrees-C, the co ntent of mRNA of the psbA gene declines sharply in the control cotyled ons and on solutions of both phytohormones. The possibility of using i solated cotyledons of yellow lupine to study the mechanism governing r egulation of the expression of chloroplast protein genes by phytohormo nes, light, and temperature is discussed in the work.