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Abstract

Two genes encoding for Late embryogenesis abundant proteins (LEAs) are expressed in encysted diapausing embryos (or resting eggs) of rotifers (Brachionus plicatilis, O.F. Müller) and females forming them. The two genes (bpa-leaa and bpa-leab) share ~50% of their nucleotides sequence and bpa-leaa is more than twice longer than bpa-leab. The deduced amino acid sequences show high abundance of alanine, glycine, lysine and glutamic acid, a hydropathy index lower than 1 and a relatively high (81-82%) predicted probability of forming α-helices in their secondary structure, characteristic features of LEAs. The predicted molecular mass of bpa-LEAA (~67kDa) and bpa-LEAB (~27 kDa) are similar to the molecular mass determined by Western-blot analyses, suggesting a low probability of post-translational modifications. In silico analysis reveals that the two LEAs resemble Group 3 LEA proteins based on the repeats for 11mermotifs, although they also display several putative amino acids typical of the 20mer-motif of Group 1 LEAs. The rotifer LEAs do not contain a predicted target sequence and are more likely localized in the cytosol. LEAs were expressed in resting eggs and females producing them, but not in other female forms or males. LEA transcripts and proteins are degraded during hatching, suggesting that LEAs are developmentally programmed during resting egg formation and hatching. LEAs probably equip the resting eggs to withstand desiccation, if encountered during dormancy. This study expands our knowledge on the biological pathways associated with formation of rotifer resting eggs and demonstrates the occurrence of LEAs also in dormant nondesiccated encysted animal embryos.