The recalcitrant plant species, Castanospermum australe and Trichilia dregeana, differ in their ability to produce dehydrin-related polypeptides during seed maturation and in response to ABA or water-deficit-related stresses

Abstract

In constrast to seeds of orthodox species, those of recalcitrant species do not acquire desiccation tolerance during their development and are shed from the parent plant at high water contents. Dehydrin production in seeds of recalcitrant species was examined during development and germination, in response to abscisic acid (ABA), and following the imposition of various water-deficit-related stresses, including desiccation, water stress, high salt, high osmolarity, and low temperature. Two tropical species exhibited a differential capacity to produce dehydrin-related proteins during seed maturation. Dehydrins were present in axes and cotyledons of Castanospermum australe seeds during mid-maturation and at maturity. In Trichilia dregeana, no dehydrin-related polypeptides were detected in the mature seed. During the development of C. australe seeds, the nature of the dehydrin-related polypeptides accumulated in the cotyledons and axis changed and new polypeptides were detected in the mature seeds that were not present during mid-maturation. The dehydrins present in cotyledons of mature seeds (31, 37 and 40 kDa) were still detectable after germination (i.e. in untreated seedlings). These dehydrins became less abundant in the cotyledons of C. australe seedlings following ABA and all stress treatments except colds although most of the dehydrins were still detectable. An exception was the desiccation-treated seedlings, in which no dehydrins were detected. In the roots of C. australe seedlings, no dehydrins were found after germination nor were they induced in the root by ABA or any of the stress treatments imposed on seedlings. Seedlings of Trichilia dregeana did not produce dehydrins in the roots or cotyledons when exposed to ABA or water-deficit-related stresses.