Streptomyces soli sp. nov., isolated from birch forest soil.

A Gram-staining positive, aerobic, non-motile, rod-shaped bacterium, designated strain LAM7114T, was isolated from soil sample collected from a birch forest in Xinjiang Uygur Autonomous Region, China. The optimal temperature and pH for the growth of strain LAM7114T were 30 °C and 7.0, respectively. Strain LAM7114T could grow in the presence of NaCl up to 10% (w/v). Comparative analysis of the 16S rRNA gene sequences revealed that LAM7114T was closely related to the members of the family genus Streptomyces, with the highest similarity to Streptomyces urticae NEAU-PCY-1T (98.3%) and Streptomyces fildesensis GW25-5T (98.2%). The genomic G + C content was 70.0 mol%. The DNA-DNA hybridization values between strain LAM7114T and S. urticae CCTCC AA 2017015T, S. fildesensis CGMCC 4.5735T were 32.5 ± 1.8% and 27.5 ± 2.6%, respectively. The cell wall contained LL-diaminopimelic acid as the diagnostic diamino acid in the peptidoglycan. The whole-cell hydrolysates included glucose and mannose. The major fatty acids were anteiso-C15:0, iso-C15:0 and iso-C16:0. The predominant menaquinones were MK-9(H6), MK-9(H4) and MK-9(H8). The main polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, three unidentified aminophospholipids, three unidentified phospholipids, and an unidentified aminolipid. Based on the phenotypic characteristics and genotypic analyses, we propose that strain LAM7114T represents a novel species in the genus Streptomyces, for which the name Streptomyces soli sp. nov. is proposed. The type strain is LAM7114T (= CGMCC 4.7581T = JCM 32822T).

Positional effects on efficiency of CRISPR/Cas9-based transcriptional activation in rice plants.

The nuclease-dead Cas9 (dCas9) has been reprogrammed for transcriptional activation by fusing dCas9 to a transcriptional activation domain. In the presence of a guide RNA (gRNA), the dCas9 fusions specifically bind to regions of a promoter to activate transcription. Significant amount of effort has been directed toward the identification and optimization of the fusions of dCas9-activation domain, but very little is known about the impact of gRNA target positions within a promoter in plants on transcriptional activation efficiency. The dCas9-6TAL-VP128 system (dCas9-TV) has been optimized to activate transcription in plants. Here we use the dCas9-TV to activate transcription of OsWOX11 and OsYUC1, two genes that cause dramatic developmental phenotypes when overexpressed. We designed a series of gRNAs targeting the promoters of the two genes. We show that gRNAs that target regions within 350 bp upstream of the transcription start site were most effective in transcriptional activation. Moreover, we show that using two gRNAs that simultaneously target two discrete sites in a promoter can further enhance transcription. This work provides guidelines for designed transcriptional activation through CRISPR/dCas9 systems.

The YUCCA-Auxin-WOX11 Module Controls Crown Root Development in Rice.

A well-developed root system in rice and other crops can ensure plants to efficiently absorb nutrients and water. Auxin is a key regulator for various aspect of root development, but the detailed molecular mechanisms by which auxin controls crown root development in rice are not understood. We show that overexpression of a YUC gene, which encodes the rate-limiting enzyme in auxin biosynthesis, causes massive proliferation of crown roots. On the other hand, we find that disruption of TAA1, which functions upstream of YUC genes, greatly reduces crown root development. We find that YUC overexpression-induced crown root proliferation requires the presence of the transcription factor WOX11. Moreover, the crown rootless phenotype of taa1 mutants was partially rescued by overexpression of WOX11. Furthermore, we show that WOX11 expression is induced in OsYUC1 overexpression lines, but is repressed in the taa1 mutants. Our results indicate that auxin synthesized by the TAA/YUC pathway is necessary and sufficient for crown root development in rice. Auxin activates WOX11 transcription, which subsequently drives crown root initiation and development, establishing the YUC-Auxin-WOX11 module for crown root development in rice.