INDIVIDUAL MEMBERS OF THE CAB GENE FAMILY DIFFER WIDELY IN FLUENCE RESPONSE

Chlorophyll a/b-binding protein genes (Cab genes) can be extremely sen sitive to light. Transcript accumulation following a red light pulse i ncreases with fluence over 8 orders of magnitude (L.S. Kaufman, W.F. T hompson, W.R. Briggs [1984] Science 226: 1447-1449). We have construct ed fluence-response curves for individual Cab genes. At least two Cab genes (Cab-8 and AB96) show a very low fluence response to a single re d light pulse. In contrast, two other Cab genes (AB80 and AB66) fail t o produce detectable transcript following a single pulse of either red or blue light but are expressed in continuous red light. Thus, very l ow fluence responses and high irradiance responses occur in the same g ene family.