THE RELATIONSHIP OF THIAMINE TO THE ALT LOCUS OF PISUM-SATIVUM L

After producing 4 to 6 normal nodes, the alt mutant of Pisum sativum L. developed chlorosis of the young leaves and apical growth ceased. Thiamine applications stimulated renewed apical growth, normal chlorophyll content, and production of viable seed. Seed recovered from thiamine-treated parents grew normally and in turn set seed. The second generation, untreated seed produced seedlings that developed symptoms characteristic of alt. Extracts of Alt seed also normalized alt, and biological activity co-chromatographed with thiamine in two HPLC systems. Tests of thiamine precursors revealed that the pyrimidine moiety normalized alt, whereas the thiazole moiety did not. The distribution and metabolism of [14C]thiamine in Alt and alt were consistent with thiamine deficiency in the mutant. We concluded that alt allele blocks biosynthesis of the pyrimidine moiety. Large capacity for storage of maternal thiamine seems to account for many of the symptoms and experimental observations described. © 1990, Gustav Fischer Verlag, Stuttgart. All rights reserved.