Characterization of mRNAs that accumulate during illumination of excised leaves of big bluegrass (Poa secunda)

Photosynthate accumulation during illumination of excised leaves provides a useful system to study some aspects of carbohydrate metabolism. The objectives of this study were to identify and characterize mRNAs that show regulated abundance during illumination of excised leaves of big bluegrass (Poa secunda). Differential display PCR identified mRNAs of interest. RNA samples from excised leaves were tested with 45 primer combinations after 0, 0.5, 2, 8, and 24 h of light exposure. Of approximately 2500 cDNA amplification products examined, only six different sequences showed repeatable patterns of regulation during the time course of these experiments. Three full-length cDNAs were isolated and none appear to be directly related to carbohydrate metabolism. The deduced amino acid sequences of the three cDNA products show homology to the thiamin biosynthesis proteins, metallothionene-like proteins and ribosomal proteins of other species. The abundance of metallothinene-like protein mRNA, in particular, showed strong up-regulation during illumination of detached leaves. The abundance of these three mRNAs in attached leaves was further evaluated under low-temperature and dehydration treatments-conditions also known to influence photosynthate/carbohydrate accumulation. The abundance of the metallothinene-like protein was strongly affected by dehydration, whereas the thiamin biosynthesis and ribosomal protein mRNAs were only somewhat affected by low temperatures.