Abstract Detail

Developmental and Structural Section

Povilus, Rebecca [1], Friedman, William [1].

Reciprocal interploidy crosses in Nymphaea thermarum (Nymphaeales) – implications for the evolution of imprinting during seed development.

Over a century of reciprocal interploidy crossing experiments in monocots and eudicots, in which diploid and autotetraploid individuals of the same species are cross-fertilized, have offered critical insights into the mechanisms that underlie flowering plant seed development. In these crosses, the ratio of maternal to paternal genome contributions to offspring tissues (embryo and endosperm) is altered. In general, endosperms with an excess of maternal genomes have a truncated early developmental phase and ultimately lead to the production of a smaller seed. In contrast, endosperms with an excess of paternal genomes appear to over-proliferate (often to the extent that seeds are aborted) and produce larger seeds. Collectively, these experiments have provided key evidence that gene imprinting, perhaps driven by interparental conflict, may have been a guiding force in the evolution of endosperm as an essential seed tissue. Making this question even more intriguing is the relatively recent observation that the vast majority of early-diverging angiosperm lineages are characterized by diploid endosperm, rather than the triploid endosperm that is common in eudicots and monocots. We take advantage of the rapid-cycling water lily, Nymphaea thermarum, to perform reciprocal interploidy crosses in a member of one of the earliest diverging angiosperm lineages (Nymphaeales). N. thermarum is uniquely amenable as an experimental system and we have successfully generated autotetraploid lines. Seeds from reciprocal interploidy crosses (4N x 2N and 2N x 4N) and homoploid (2N x 2N) control crosses were collected and total seed size measured, along with the sizes of the endosperm and the embryo. Differences in growth and developmental patterning of these seed constituents confirm the general pattern of reciprocal phenotypes of maternal- and paternal-excess crosses noted in monocots and eudicots. This implies that the ratio-dependent relationship between maternal and paternal genomes likely existed early in the evolutionary history of endosperm, and that some of the underlying molecular mechanisms for parent-of-origin gene imprinting operated during seed development at the outset of angiosperm diversification.

1 - Harvard University, Arnold Arboretum, Organismic and Evolutionary Biology, 1300 Centre Street, Boston, MA, 02131, USA

Keywords:
Nymphaeales
Endosperm
Seed Development
Imprinting
Interploidy Crosses
Water lily.

Presentation Type: Oral Paper:Papers for Sections
Session: 45
Location: Salon 11/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 2:15 PM
Number: 45004
Abstract ID:646
Candidate for Awards:Maynard F. Moseley Award