Antheridiogen and abscisic acid affect conversion and ANI1 expression in Ceratopteris richardii gametophytes

Abstract

The development of male Ceratopteris richardii Brongn. gametophytes (induction) is well studied. Males develop in response to hermaphrodite-produced antheridiogen, which coincides with induced expression of ANI1 (antheridiogen-induced 1). Induction is blocked by exogenous abscisic acid (ABA). Conversion of male gametophytes to hermaphrodites occurs when males are removed from antheridiogen and is a less understood process. In this study, males were exposed to ABA at 0 μmol·L−1, 1 μmol·L−1, 10 μmol·L−1, 100 μmol·L−1, and 300 μmol·L−1 and monitored for conversion. RT-qPCR methodology was developed to examine ANI1 expression levels in gametophytes outside of induction. Conversion of male gametophytes occurred more often and more quickly in media lacking ABA, and at lower ABA concentrations than at higher concentrations. ANI1 expression dropped significantly in males transferred to media lacking antheridiogen, but remained high in males remaining in the presence of antheridiogen and in those transferred to ABA. ANI1 expression was higher in 24 day old hermaphrodites relative to 24 day old males and at comparable expression levels to 6 day old gametophytes. These results suggest ABA serves a distinct role in conversion compared with induction, and ANI1 is expressed throughout the male’s lifespan and in older hermaphrodites.