STEELE, K. P.*, L. YANG, M. SABIR, AND M. F. WOJCIECHOWSKI. Department of Biology, California State University, Hayward, CA 94545, and Section of Evolution and Ecology, University of California, Davis, CA 95616. - Phylogenetic relationships of the tribes Trifolieae and Vicieae (Fabaceae) using sequences of Mendel's stem length gene, Le.
The nuclear gene Le, the original stem length gene studied by
Gregor Mendel, encodes 3B-hydroxylase, a key enzyme in the gibberellic
acid biosynthetic pathway. Nucleotide sequences of this single copy
nuclear gene were used for phylogenetic analyses of representatives of
genera traditionally included in the Trifolieae and Vicieae, with
representatives of tribes Cicereae and Galegeae used as outgroups.
This gene consists of two exons of approximately 1.1 Kb with a large
intron of about 544 bp. Exon sequences are sufficiently conserved to
be useful for analyses of genera within these two tribes. Intron
sequences are useful only for analyses within genera. Consistent with
our earlier results from analyses of matKsequences for these
taxa, Medicago, as defined by floral characters associated with
an explosive pollination syndrome, forms a well-supported monophyletic
group distinct from that formed by Melilotuswhich is nested
within Trigonella. Trifoliumis basal to the remainder of
Trifolieae (excepting Parochetus). Within Vicieae
Viciais basal to Pisumand Lathyrus. Phylogenetic
analyses of these sequence data provide a framework to consider
hypotheses about the evolution of trifoliate leaves and floral and
fruit characteristics in these clades.
Key words: 3Beta-hydroxylase, Fabaceae, phylogeny, stem length gene Le, Trifolieae, Vicieae