Effects of Bacteria on Timing of Male to Hermaphrodite Conversion in Gametophytes of the Fern Ceratopteris richardii

Abstract:

Gametophytes of the fern Ceratopteris richardii may be either hermaphrodite or male.  Hermaphrodites secrete a hormone called antheridiogen (A_CE) into the environment that influences developing gametophytes to develop as male, while the absence of A_CE tends to lead to hermaphrodite development.  If males are removed from the influence of A_CE, they convert to hermaphrodites.  Previous experiments have shown that the gram-negative soil bacterium, Pseudomonas nitroreducens, can alter sex determination by increasing the number of hermaphrodites in culture.  Here we ask whether P. nitroreducens can alter the timing of male to hermaphrodite conversion.  Males were grown for 14 days in the presence of hermaphrodites and A_CE.  The males were then transplanted into individual Petri dishes containing or lacking P. nitroreducens.  Males in the presence of P. nitroreducens converted significantly earlier to hermaphrodites.  This suggests that there may be similarities in the mechanism of hermaphrodite sex determination and male to hermaphrodite conversion.  Conversion experiments with other gram-negative soil bacteria, including Pantoea vagans and Aeromonas eucrenophila, and two gram-positive soil bacteria, including Prestia aryabhattai and Lysinibacillus xylanilyticus, are currently underway.