No abstract

OsPPR6, a pentatricopeptide repeat protein involved in editing and splicing chloroplast RNA, is required for chloroplast biogenesis in rice. The chloroplast has its own genetic material and genetic system, but it is also regulated by nuclear-encoded genes. However, little is known about nuclear-plastid regulatory mechanisms underlying early chloroplast biogenesis in rice. In this study, we isolated and characterized a mutant, osppr6, that showed early chloroplast developmental defects leading to albino leaves and seedling death. We found that the osppr6 mutant failed to form thylakoid membranes. Using map-based cloning and complementation tests, we determined that OsPPR6 encoded a new Pentatricopeptide Repeat (PPR) protein localized in plastids. In the osppr6 mutants, mRNA levels of plastidic genes transcribed by the plastid-encoded RNA polymerase decreased, while those of genes transcribed by the nuclear-encoded RNA polymerase increased. Western blot analyses validated these expression results. We further investigated plastidic RNA editing and splicing in the osppr6 mutants and found that the ndhB transcript was mis-edited and the ycf3 transcript was mis-spliced. Therefore, we demonstrate that OsPPR6, a PPR protein, regulates early chloroplast biogenesis and participates in editing of ndhB and splicing of ycf3 transcripts in rice.

Fourier ptychography (FP) is a promising computational imaging technique that overcomes the physical space-bandwidth product (SBP) limit of a conventional microscope by applying angular-varied illuminations. However, to date, the effective imaging numerical aperture (NA) achievable with a commercial LED board is still limited to the range of 0.3-0.7 with a 4 × /0.1NA objective due to the geometric constraint with the declined illumination intensities and attenuated signal-to-noise ratio (SNR). Thus the highest achievable half-pitch resolution is usually constrained between 500-1000 nm, which cannot meet the requirements of high-resolution biomedical imaging applications. Although it is possible to improve the resolution by using a high-NA objective lens, the FP approach is less appealing as the decrease of field-of-view (FOV) will far exceed the improvement of spatial resolution in this case. In this paper, we initially present a subwavelength resolution Fourier ptychography (SRFP) platform with a hemispherical digital condenser to provide high-angle programmable plane-wave illuminations of 0.95NA, attaining a 4 × /0.1NA objective with the final effective imaging performance of 1.05NA at a half-pitch resolution of 244 nm with the incident wavelength of 465 nm across a wide FOV of 14.60 mm, corresponding to a SBP of 245 megapixels. Our work provides an essential step of FP towards high-throughput imaging applications.

No abstract

Abstract-Non-line-of-sight (NLOS) propagation is one of the major barriers to accurate ranging and positioning based on time of arrival (TOA) in the application of an ultra wideband (UWB) system. This paper proposes a new method for NLOS identification and mitigation based on signal characteristic analysis and fuzzy theory. This method neither requires to build a statistical model nor to create and update a training database, so that it can be used conveniently for different application scenarios. Extensive experiments were conducted and the results show that the cumulative distribution function of the ranging error below 0.5 meter is over 90% when using the proposed mitigation method, while that without using the mitigation method is below 70%. Also, by using the proposed method, the root mean square error (RMSE) of the range measurements is reduced from 0.77 to 0.33 meter. The results demonstrate that this method can effectively identify NLOS and mitigate the NLOS-induced ranging error.