Starch-accumulating (S-type) sieve-element plastids in Hydatellaceae: implications for plastid evolution in flowering plants

• DOI: 10.1007/s00709-009-0067-2
• Publication Date: 2009-08-06T07:12:21Z
• Authors: Julia Tratt; Christina J. Prychid; H.-Dietmar Behnke; Paula J. Rudall
• Keywords: 0106 biological sciences; Magnoliopsida; Starch; Plastids; 01 natural sciences; Phylogeny

TEM investigation of sieve-element plastids in three species of Trithuria, the sole genus of the small aquatic family Hydatellaceae, show that P-type plastids are absent from this genus and only starch-accumulating (S-type) sieve-element plastids are present. This discovery is consistent with the recent transfer of Hydatellaceae from the highly derived monocot order Poales (grasses and their allies) to the early-divergent angiosperm order Nymphaeales (waterlilies) based on molecular phylogenetic data. Species of Poales consistently possess P2-subtype plastids, in common with other monocots, but only S-type plastids are present in Nymphaeales. The results confirm that Hydatellaceae do not belong in monocots. Optimisation of the two major types of sieve-element plastid onto a recent phylogeny of early-divergent angiosperms confirms that S-type is the primitive form and indicates that P-type sieve-element plastids have evolved more than once in angiosperms.