Abstract:
A polyclonal antibody was used to detect the expression of the homeodomain protein Lim1 (Lhx1) in embryos of Xenopus laevis, Engystomops randi, Colostethus machalilla and Gastrotheca riobamabae. These frogs belong to four separate families, and have differences in their modes of reproduction and developmental rates. The expression of Lim 1 in embryos of these frogs resembled the X. laevis expression pattern. Thus, the dorsal blastopore lip, axial mesoderm, pronephros and certain cells of the central nervous system were Lim1-postive in embryos of all frogs. There were, however, time differences; thus, in the mid-gastrula of the rapidly developing embryos of X. laevis and E. randi, the Lim1 protein was simultaneously detected in the prechordal plate (head organizer) and notochord (trunk organizer). In contrast, only the prechrodal plate was Lim1- positive during gastrulation in the slow developing embryos of C. machalilla. The notochord elongated and became Lim-1 positive after closure of the blastopore in C. machalilla and G. riobambae embryos. The prechordal plate of G. riobambae embryos could not be clearly detected, as the Lim 1-signal remained around the blastopore during gastrulation. These observations indicate that the timing of gene expression at the dorsal blastopore lip in embryos of slow developing frogs differs from that of X. laevis. Moreover, the comparison shows that the developmental processes of the head and trunk organizers are basically separable and become dissociated in embryos of the slow developing frog, C. machalilla.
