Poster: Seed biology

Abs # 717: Communication between generations during seed development influences germination.

Presenter:	Downie, Bruce , adownie@uky.edu
Authors	Downie, Bruce  (A)
Affiliations:	(A): University of Kentucky

The three brownseed (bs¹, ², ⁴) and the blackseed (bks) mutants of the model plant tomato (Lycopersicon esculentum) are inherited as recessive, Mendelian traits in reciprocal crosses. In contrast, testa attributes of tomato anthocyaninless and Arabidopsis thaliana transparent testa mutants are inherited according to the genotype of the testa. The bks and bs mutants accumulate a dark pigment in the cell layers of the testa. The bs⁴ mutant also accrues a testa-like pigment in the periclinal wall of the most exterior endosperm cell layer. The poor germination performance of the bks, bs¹, and possibly the bs² mutant seeds is due to a greater impediment of the mutant testae to radicle egress, relative to wild type, while the bs⁴ mutant testa was not significantly stronger than wild type. Rather, a survey of the bs⁴ mutant transcriptome during late development, quiescence and during germination revealed it does not exit the developmental program. Consequently, while imbibition on GA₄₊₇ did not ameliorate the germination percentage or speed of bs¹, bs², or bks mutant seeds, relative to their performance on water, those of bs⁴ were stimulated to complete germination faster and to a greater percentage. Efforts to identify the components of the melanic compound accumulating in the bks mutant testa, to acquire transposon tagged mutants of any bks or bs mutant, and to fine map and walk to bs¹ are ongoing. The bs and bks mutants have unveiled a communication between generations during seed development, the older generation represented by the testa, and the younger by the endosperm/embryo which can exert some control over the degree to which the testa toughens and thus influence the subsequent percentage of progeny that can complete germination.