The greening process in cress seedlings IV. Light regulated expression of single Lhc genes

Abstract

Transcript levels of single Lhc genes were determined in etiolated cress seedlings ( Lepidium sativum L.) after various irradiations. Hybridization probes used in this study specifically detected transcripts of three Lhcb1 genes (probes cd1, cd2, cd3), one Lhcb2 gene (probe cd4), one Lhcb3 gene (probe cd5) and one Lhcb3 gene (probe 6). A 2 min pulse of red light resulted in a transient increase in the steady-state level of all transcripts determined for up to 10 h after the light pulse. Light induction was stronger in 4 day old than in 3 day old seedlings. The maximum of light induction was generally reached 4 h after a pulse of red light except for Lchb2 and Lchb3 transcripts that exhibited a maximum already 2 h after the light pulse. The relationship between red, blue and far-red irradiation was similar for all investigated Lhc genes: transcrip levels were 75–85% after a 30 min blue and 60–70% after a 30 min far-red pulse, compared with the red pulse = 100%. The contribution of the photoreceptor phytochrome and the physiological role of different kinetics of expression are discussed.