Tribolium mae expression suggests roles in terminal and midline patterning and in the specification of mesoderm

In Drosophila, the Mae protein ("modulator of the activity of Ets") regulates receptor tyrosine kinase (RTK)-dependent mitogen-activated protein kinase (MAPK) signaling. Mae has been shown to bind the Yan and Pointed-P2 transcription factors, thereby changing their ability to activate or repress target genes. In this work we show that the mae ortholog of the red flour beetle Tribolium castaneum (Tc'mae) is active at the posterior, but not the anterior pole of the blastoderm. Since MAPK signaling is known to be active at both poles, Tc'Mae could function to modulate terminal MAPK signaling to differentiate the developmental programs at the anterior and posterior poles of the Tribolium blastoderm embryo. Tc'mae is also expressed along the midline of the germband, similar as in Drosophila, where it is involved in the patterning of midline cells. Before gastrulation and in the growth zone, Tc'mae is active in mesoderm precursor cells. This suggests that in short germ embryos MAPK signaling may also be involved in the specification of mesoderm.