Background Chloroplast biogenesis, a complex process in higher plants, is the key to photoautotrophic growth in plants. White virescent ( wv ) mutants have been used to unfold the molecular mechanisms underlying the regulation of chloroplast development and chloroplast gene expression in plants. However, most of genes controlling white virescent phenotype still remain unknown. Results In this study, we identified a temperature- and light intensity-sensitive mutant, named as wv . The content of chlorophyll was dramatically decreased in the immature leaves of wv mutant under the conditions of low temperature and high-light intensity. TEM observation showed that the chloroplasts in the young leaves of wv mutant lacked an organized thylakoid membrane, whereas crescent-shaped chloroplasts with well-developed stromal and stacked grana thylakoids in the mature leaves were developed. Immunoblot analyses suggested that proteins of photosynthetic complexes were decreased substantially in wv mutants. Based on map-based cloning and transgenic analysis, we determined that the wv phenotype was caused by single base mutation in the first intron of WV gene, which encoded a thioredoxin protein with 365 amino acids. qRT-PCR analysis revealed that the expression of WV gene was significantly down-regulated in wv mutant. In addition, knockdown of WV gene through RNAi also resulted in white virescent young leaves, suggesting that the mutation possibly blocks the differentiation of chloroplasts through inhibiting the expression of WV gene. Furthermore, the expression of WV peaked in apical buds and gradually decreased along with the developmental stage, which was consistent with the wv mutant phenotype. Expression analysis of chloroplast-encoded genes by qRT-PCR showed that the wv mutation affected the expression pattern of chloroplast-encoded PEP dependent genes. Conclusion Our results suggested that wv mutant was sensitive to low temperature and light intensity. WV gene was essential for chloroplast differentiation. A single base mutation in the first intron resulted in down-regulation of WV gene expression, which inhibited the expression of chloroplast-encoded genes, thereby blocking chloroplast formation and chlorophyll synthesis. Electronic supplementary material The online version of this article (10.1186/s12870-019-1829-4) contains supplementary material, which is available to authorized users.

A simple yet powerful approach to obtain structural color is the amorphous assembly of colloidal spheres, which is also referred to as the amorphous photonic structure or photonic glasses (PGs). Additionally, the functionalization of the colloidal spheres as building blocks can further endow the resulting PGs with multifunctions. Herein, we have developed a facile strategy to prepare SiO2 colloidal spheres with concentrically embedded carbon dots (CDs). Notably, the CDs are prepared and silane-functionalized simultaneously, which enables the perfect incorporation of CDs into the Si–O network during the Stöber reaction and thus leads to the formation of a concentric SiO2/CD interlayer within the obtained SiO2 spheres. Moreover, the obtained SiO2/CD spheres can be applied as photonic pigments by assembling them into PGs, which exhibit structural color under daylight and fluorescence under UV illumination. With incorporation of carbon black, the structural color saturation and fluorescence intensity can be further manipulated. Owing to the combination of structural colored PGs and fluorescent CDs, our study can offer inspiration for color- and fluorescence-related applications such as sensing, in vivo imaging, LEDs, and anticounterfeiting.

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Fiber Bragg grating (FBG) array, consisting of a number of sensing units in a single optical fiber, can be practically applied in quasi-distributed sensing networks. Serious signal crosstalk occurring between large-serial of identical FBGs, however, has limited the further increase in the number of sensing units, thus restricting applications only for short-distance sensing networks. To reduce the signal crosstalk, we design two novel types of 10-kilometer-long FBG arrays with 10 000 equally spaced gratings, written on-line using a customized grating inscription system, which is affiliated to a drawing tower. Main factors causing signal crosstalk, such as spectral shadowing and multiple reflections, are firstly investigated in theory. Consistent with the theoretical findings, experimental results are proving that ultra-weak (the reflectivity of ∼−40 dB) and multi-wavelength gratings of a number more than 10 000 can be readily identified, with satisfied low crosstalk. The maximum attenuation of grating signal and minimum signal-to-noise ratio (SNR) in a single-wavelength array are 10.69 dB and 5.62 dB, respectively. As a comparison, by increasing the number of central wavelengths to three, the attenuation can be effectively reduced to 5.54 dB and the minimum SNR has been improved to 8.14 dB. The current study significantly enhances the multiplexing capacity of FBG arrays and demonstrates promising potentials for establishing large-capacity quasi-distributed sensing networks.

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