CHARACTERIZATION OF TAGETES-PATULA CDNA CLONES OBTAINED BY DIFFERENTIAL SCREENING IN RELATION TO THIOPHENE BIOSYNTHESIS

In an attempt to isolate genes involved in thiophene metabolism, a cDN A library was constructed from poly(A)(+) RNA of a thiophene-producing root culture of Tagetes patula and differentially screened against a cDNA probe prepared from poly(A)+ RNA of leaves, which are low in thio phenes. Five cDNA clones were selected for expression and sequence ana lysis. Two clones, containing previously unknown sequences, revealed t he accumulation of gene transcripts in roots and hypocotyls but not in leaves of both Tagetes species. Since thiophenes predominantly accumu lated in roots and hypocotyls, it is concluded that with respect to tr anscript distribution, the genes corresponding to these two clones are expressed as expected for genes of thiophene biosynthesis. However, i n roots, the steady-state levels of the transcripts detected by both c lones did not reflect the differences in thiophene content and thiophe ne synthesizing capacity, indicating that the corresponding genes are not involved in rate-limiting steps of the secondary pathway. Three cD NA clones showing homology to pathogenesis-related proteins of the Bet ul-type revealed the accumulation of transcripts exclusively in roots of T. patula and T. erecta.