The complete chloroplast genome of Salix lindleyana (salicaceae), a plateau plant species.

Salix lindleyana Wallich ex Andersson 1851 is a species of genus Salix which mainly grows on mountains above 3000 m at sea level in Qinghai-Tibetan Plateau (including the Himalayas and Hengduan Mountains). To determine its phylogenetic position within Salix, we reconstructed S. lindleyana complete chloroplast (cp) genome sequence by de novo assembly using whole-genome sequencing data. The completed chloroplast genome was 155,304 bp, with a total GC content of 36.7%. It had a very typical tetrad structure, including a large single-copy (LSC) region of 84,539 bp, a small single-copy (SSC) region of 16,161 bp, and two inverted repeats (IR) regions of 27,302 bp. A total of 132 functional genes were distributed in the chloroplast genome, including 87 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. Phylogenetic analysis showed that S. lindleyana was clustered with Salix dasyclados Wimmer 1849 and Salix variegata Franchet 1887. The complete chloroplast genome of S. lindleyana provides potential genetic resources for further phylogenetic studies.

Non-synonymous substitution of evolutionarily conserved residue in Tau class glutathione transferases alters structural and catalytic features.

Plant-specific tau glutathione transferases (GSTs) are basically involved in catalysing γ-glutathione (GSH)-dependent conjugation reactions with pesticides and herbicides, which play an important role in the detoxification of pollutants. Given the lack of systematic biochemical and structural information on tau GSTs, the study of their mediated defence mechanisms against toxic compounds has been greatly hindered. Here, we reveal the importance of the Ile residue closely interacting with GSH for the structural stability and catalytic function of GST. Evolutionary conservation analysis indicated that the crucial G-site Ile55 in the SbGSTU6 was converted to Thr53 of SbGSTU7. The comparative biochemical data on SbGSTU6, SbGSTU7 and their mutants showed that the substitution of Ile by Thr caused significant decrease in the affinity and catalytic efficiency of the GSTs. The unfavourable structural flexibility and pKa distribution of the active cavity residues were also demonstrated. Crystallography studies and molecular dynamics simulations showed that the conversion resulted in the hydrogen bond recombination with GSH and conformational rearrangement of GST active cavity, in which the Ile residue was more conducive to the formation of enzyme substrate complexes. The extensive biochemical and structural data not only reveal the critical role of the conserved G-site Ile residue in catalysing GSH-conjugate reactions but also provide valuable resources for the development of GST engineering in analytical and agricultural biotechnology.