Summary/model.

<p>Bold arrows delineate the new findings in this paper. The Drosophila male accessory gland consists of two secretory cell types: main cells and secondary cells. Main cells produce seminal proteins essential for inducing post-mating responses (PMR) in mated females; the function (if any) of secondary cells was unknown. Sex Peptide (SP) from the main cells induces many aspects of PMR, but persistence of its effects requires other seminal proteins (the LTR machinery: CG9997, CG17575, CG1652 and CG1656), whose cellular source was unknown. Here, we showed that the Hox gene <i>Abd-B</i> is essential for normal development of the secondary cells, but with regulatory characteristics (not shown in this figure) that differ from those used in segment identity. By deleting the secondary-cell regulatory element of <i>Abd-B</i>, we obtained males with abnormal secondary cells. Mates of those males failed to maintain the PMR, indicating that secondary cells play an essential role in reproduction: their products, along with main cell products, allow persistence of SP in mated females, thus prolonging their post-mating responses.