Agroecosystem management for rare species of Paysonia (Brassicaceae): integrating their seed ecology and life cycle with cropping regimens in a changing climate

Dormancy break and germination of seeds are governed by climatic cues, and predicted changes in climate may impact the ecology and conservation of species. Paysonia perforata and P. stonensis are rare brassicaceous winter annuals occurring primarily in fields on floodplains, where corn or soybeans are recommended for habitat maintenance. We tested the effects of precipitation, based on two predictions of changes in climate, on seed germination in these two species and placed the results into a management framework. Seeds of both species, collected during peak dispersal in late April/early May, were given various periods of light (or darkness) followed by darkness (or light) at summer temperatures before placement in darkness during late summer/early autumn in both laboratory and field. The light requirement was met earliest at 10 wk (mid-July) on alternating wet/dry substrate (simulating current climatic conditions). However, seeds of P. perforata and P. stonensis were photostimulated earliest at 2 wk (mid-May) and 6 wk (mid-June), respectively, on a continuously moist substrate (simulating predicted future conditions). The soil seed bank could be depleted if plowing coincides with photostimulation of seeds. Fields should be prepared after dispersal but before seeds are photostimulated and harvesting completed before seed germination in early September. Because seeds are highly photostimulated in late summer, disturbance from harvesting must be low to prevent burial. Cultivation of soybean, particularly for forage, is better matched to the seed biology and life cycle of Paysonia than that of corn under current and predicted climates.     

Chaperonin genes on the rise: new divergent classes and intense duplication in human and other vertebrate genomes

Background  

Chaperonin proteins are well known for the critical role they play in protein folding and in disease. However, the recent identification of three diverged chaperonin paralogs associated with the human Bardet-Biedl and McKusick-Kaufman Syndromes (BBS and MKKS, respectively) indicates that the eukaryotic chaperonin-gene family is larger and more differentiated than previously thought. The availability of complete genome sequences makes possible a definitive characterization of the complete set of chaperonin sequences in human and other species.     

Embryo growth and dormancy in seeds of six Hosta species native to Korea

Although it has been speculated that Hosta seeds have an underdeveloped embryo and morphological (MD) or morphophysiological dormancy (MPD), no detailed studies have been carried out to definitively confirm this suggestion. Our first purpose was to determine if embryos of six Korean species of Hosta (H. capitata, H. clausa, H. jonesii, H. minor, H. venusta and H. yingeri) grew inside the seeds prior to germination (i.e., were underdeveloped) or did not do so (i.e., were fully developed). Our second purpose was to identify the class of dormancy found in these seeds by examining germination during incubation at 15 and/or 25°C. The initial embryo : seed ratio in seeds of the six Hosta species was between 0.78 and 0.85, and embryos elongated by 9.6 to 17.5% prior to germination. Seeds of H. capitata, H. clausa, H. venusta and H. yingeri germinated to ≥65% in light and darkness at 15 and 25°C within 30 days, those of H. minor germinated to ≥80% in light and darkness at 25°C and to 24% in light and 50% in darkness at 15°C, and those of H. jonesii germinated to 100% in light at 25°C. We conclude that embryos in seeds of these six Hosta species are underdeveloped at maturity. Because high percentages of H. capitata, H. clausa, H. venusta and H. yingeri seeds germinated at cold and warm temperatures within 30 days, they have MD. On the other hand, seeds of H. minor germinated to high and low percentages at warm and cold temperatures, respectively. Thus, some seeds have MD and others may have MPD.