Poster: Organelle biogenesis

Abs # 636: Mutations affecting plastid development in Arabidopsis embryos

Presenter:	Ruppel, Nicholas J, nruppel@bio.indiana.edu
Authors	Ruppel, Nicholas J (A)   Logsdon, Charles  (A)   Hangarter, Roger P (A)
Affiliations:	(A): Indiana University

An Arabidopsis embryo proceeds through several well-defined stages from a single-celled zygote to a fully mature embryo. During the globular stage of embryogenesis, green chloroplasts develop that can contribute to the production of storage reserves that are used as an energy source during seedling germination and growth. Prior to the final stages of embryo maturation, the chloroplasts dedifferentiate into basal-state eioplasts by decreasing in volume and losing their chlorophyll, thylakoid membranes, and starch. Upon germination, eioplasts can redevelop into chloroplasts within embryo-derived cotyledon and hypocotyl cells, and function as an energy source and site of essential metabolic activity during seedling establishment. We have identified a novel class of Arabidopsis mutants termed spd (seedling plastid development) that affect plastid development in embryo-derived cells. The mutants exhibit cotyledon and hypocotyl albinism upon germination due to improper chloroplast development, whereas cells derived from the shoot apical meristem appear to develop normal chloroplasts. In the spd1 mutant, amyloplast development is also disrupted, which attenuates the gravitropic response. Precociously germinated spd embryos do not display the albinism phenotype, implicating the mutation as a product of either late embryo maturation or seedling germination. Our analyses of the developmental and physiological defects associated with the spd mutations are providing new insights into the critical stages of plastid development that are an integral part of the embryo maturation program.