NEAR-ISOGENIC LINES OF MAIZE DIFFERING FOR GLYCINEBETAINE

A series of near-isogenic glycinebetaine-containing and -deficient F-8 pairs of Zea mays L. (maize) lines were developed. The pairs of lines differ for alternative alleles of a single locus; the wild-type allel e conferring glycinebetaine accumulation is designated Bet1 and the mu tant (recessive) allele is designated bet1. The near-isogenic lines we re used to investigate whether glycinebetaine deficiency affects the p ool size of the glycinebetaine precursor, choline, using a new method for glycinebetaine and choline determination: stable isotope dilution plasma desorption mass spectrometry. Glycinebetaine deficiency in maiz e was associated with a significant expansion of the free choline pool , but the difference in choline pool size was not equal to the differe nce in glycinebetaine pool size, suggesting that choline must down-reg ulate its own synthesis. Consistent with this, glycinebetaine deficien cy was also associated with the accumulation of the choline precursor, serine. A randomly amplified polymorphic DNA marker was identified th at detects the bet1 allele. In 62 F-8 families tested the 10-mer prime r 5'-GTCCTCGTAG produced a 1.2-kb polymerase chain reaction product on ly when DNA from Bet1/bet1 or bet1/bet1 lines was used as template. Al l 26 homozygous Bet1/Bet1 F-8 families tested were null for this marke r.