Association of Protective Proteins with Dehydration and Desiccation of Orthodox and Recalcitrant Category Seeds of Three Acer Genus Species

Mature and dried seeds from three species of the Acer genus, which differed in desiccation tolerance, were analyzed. The three species investigated were as follows: Acer platanoides L. (Norway maple, orthodox, A1 and A2 seedlots); Acer pseudoplatanus L. (sycamore, recalcitrant, B1 and B2 seedlots); and Acer saccharinum (silver maple, recalcitrant, C1 and C2 seedlots). We compared the appearance of dehydrins and small heat shock proteins in seedlots originating from cropping years that differed in weather conditions, which were monitored in detail during seed development. The experiments showed that three main dehydrins with approximate molecular weights of 46, 35, and 23 kDa were characteristic of all examined Acer species seeds. The three proteins were present in the A1 and A2 seedlots of the orthodox category Norway maple seeds and were noted either individually or together in the B1, B2, C1, and C2 seedlots of recalcitrant category seeds. It was found that one major small heat shock protein existed with a molecular mass of 22 kDa and was detectable at high concentrations in all seeds of the studied Acer species; after the seeds were dried, the content of this protein significantly increased. The potential modulation of dehydrin expression by environmental factors such as developmental heat sum and rainfall is discussed in the present work. The influence of water removal, which is caused by seed drying, in seeds of the same genus and belonging to the orthodox and recalcitrant categories is also explored.