Search

Most organisms have internal circadian clocks that mediate responses to daily environmental changes in order to synchronize biological functions to the correct times of the day. Previous studies have focused on plants found in temperate and sub-tropical climates, and little is known about the circadian transcriptional networks of plants that typically grow under conditions with relatively constant day lengths and temperatures over the year. In this study we conducted a genomic and computational analysis of the circadian biology of Carica papaya, a tropical tree. We found that predicted papaya circadian clock genes cycle with the same phase as Arabidopsis genes. The patterns of time-of-day overrepresentation of circadian-associated promoter elements were nearly identical across papaya, Arabidopsis, rice, and poplar. Evolution of promoter structure predicts the observed morning- and evening-specific expression profiles of the papaya PRR5 paralogs. The strong conservation of previously identified circadian transcriptional networks in papaya, despite its tropical habitat and distinct life-style, suggest that circadian timing has played a major role in the evolution of plant genomes, consistent with the selective pressure of anticipating daily environmental changes. Further studies could exploit this conservation to elucidate general design principles that will facilitate engineering plant growth pathways for specific environments. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s12042-008-9020-3) contains supplementary material, which is available to authorized users.

Recent advances in far-field fluorescence microscopy have led to substantial improvements in image resolution, achieving a near-molecular resolution of 20 to 30 nanometers in the two lateral dimensions. Three-dimensional (3D) nanoscale-resolution imaging, however, remains a challenge. We demonstrated 3D stochastic optical reconstruction microscopy (STORM) by using optical astigmatism to determine both axial and lateral positions of individual fluorophores with nanometer accuracy. Iterative, stochastic activation of photoswitchable probes enables high-precision 3D localization of each probe, and thus the construction of a 3D image, without scanning the sample. Using this approach, we achieved an image resolution of 20 to 30 nanometers in the lateral dimensions and 50 to 60 nanometers in the axial dimension. This development allowed us to resolve the 3D morphology of nanoscopic cellular structures.

Plantable tidal flat is one of the most important factors affecting the survival rate of mangroves seedlings in forestation. In this paper, an experiment was conducted in the tidal zones of Umbrette Natural Reserve in the Dayu Island of Xiamen in May 2003 to investigate the critical tidal level for Kandelia candel forestation. The results showed that the tidal level of 0.99 m above the zero tidal level of the Huang Ocean was not suitable for planting K. candel seedlings, because the waterlogging time at this tidal level was longer than 8 h per-tide-cycle, and the survival rate was lower than 50% . At 1.62 m above the zero tidal level of Huang Ocean, K. candel seedlings had the best growth and the highest photosynthetic assimilation, with a survival rate of 90%. At 1.31 m above the zero tidal level of Huang Ocean, K. candel seedlings could still grow well. It could be concluded that the tidal level of 1.62 m was optimal for planting K. candel seedlings, and the critical tidal level of K. candel seedlings in the coastal areas of Xiamen was not lower than 1.31 m above the zero tidal level of Huang Ocean, where the waterlogging time was not longer than 5.6 h per-tide-cycle.