RESUMO
Cyanobacteria, one of the most widespread photoautotrophic microorganisms on Earth, have evolved an inorganic CO2-concentrating mechanism (CCM) to adapt to a variety of habitats, especially in CO2-limited environments. Leptolyngbya boryana, a filamentous cyanobacterium, is widespread in a variety of environments and is well adapted to low-inorganic-carbon environments. However, little is currently known about the CCM of L. boryana, in particular its efficient carbon fixation module. In this study, we isolated and purified the cyanobacterium CZ1 from the Xin'anjiang River basin and identified it as L. boryana by 16S rRNA sequencing. Genome analysis revealed that L. boryana CZ1 contains ß-carboxysome shell proteins and form 1B of Rubisco, which is classify it as belonging to the ß-cyanobacteria. Further analysis revealed that L. boryana CZ1 employs a fine CCM involving two CO2 uptake systems NDH-13 and NDH-14, three HCO3- transporters (SbtA, BicA, and BCT1), and two carboxysomal carbonic anhydrases. Notably, we found that NDH-13 and NDH-14 are located close to each other in the L. boryana CZ1 genome and are back-to-back with the ccm operon, which is a novel gene arrangement. In addition, L. boryana CZ1 encodes two high-affinity Na+/HCO3- symporters (SbtA1 and SbtA2), three low-affinity Na+-dependent HCO3- transporters (BicA1, BicA2, and BicA3), and a BCT1; it is rare for a single strain to encode all three bicarbonate transporters in such large numbers. Interestingly, L. boryana CZ1 also uniquely encodes two active carbonic anhydrases, CcaA1 and CcaA2, which are also rare. Taken together, all these results indicated that L. boryana CZ1 is more efficient at CO2 fixation. Moreover, compared with the reported CCM gene arrangement of cyanobacteria, the CCM-related gene distribution pattern of L. boryana CZ1 was completely different, indicating a novel gene organization structure. These results can enrich our understanding of the CCM-related gene arrangement of cyanobacteria, and provide data support for the subsequent improvement and increase in biomass through cyanobacterial photosynthesis.
RESUMO
Quantifying the contributions of climate change (CC) and human activities (HA) to vegetation change is crucial for making a sustainable vegetation restoration scheme. However, the effects of extreme climate and time-lag and -accumulation effects on vegetation are often ignored, thus underestimating the impact of CC on vegetation change. In this study, the spatiotemporal variation of fractional vegetation cover (FVC) from 2000 to 2019 in northern China (NC) as well as the time-lag and -accumulation effects of 15 monthly climatic indices, including extreme indices, on the FVC, were analyzed. Subsequently, a modified residual analysis considering the influence of extreme climate and time-lag and -accumulation effects was proposed and used to attribute the change in the FVC contributed by CC and HA. Given the multicollinearity of climatic variables, partial least squares regression was used to construct the multiple linear regression between climatic indices and the FVC. The results show that: (1) the annual FVC significantly increased at a rate of 0.0268/10a from 2000 to 2019 in all vegetated areas of NC. Spatially, the annual FVC increased in most vegetated areas (â¼81.6 %) of NC, and the increase was significant in â¼54.6 % of the areas; (2) except for the temperature duration (DTR), climatic indices had no significant time-lag effects but significant time-accumulation effects on the FVC change. The DTR had both significant time-lag and -accumulation effects on the FVC change. Except for potential evapotranspiration and DTR, the main temporal effects of climatic indices on the FVC were a 0-month lag and 1-2-month accumulation; and (3) the contributions of CC and HA to FVC change were 0.0081/10a and 0.0187/10a in NC, respectively, accounting for 30.2 % and 69.8 %, respectively. HA dominated the increase in the FVC in most provinces of NC, except for the Qinghai and Neimenggu provinces.
