Han-Bo Zhang

Improved tolerance of maize (Zea mays L.) to heavy metals by colonization of a dark septate endophyte (DSE) Exophiala pisciphila

Dark septate endophytes (DSE) are ubiquitous and abundant in stressful environments including heavy metal (HM) stress. However, our knowledge about the roles of DSE in improving HM tolerance of their host plants is poor. In this study, maize (Zea mays L.) was inoculated with a HM tolerant DSE strain Exophiala pisciphila H93 in lead (Pb), zinc (Zn), and cadmium (Cd) contaminated soils. E. pisciphila H93 successfully colonized and formed typical DSE structures in the inoculated maize roots. Colonization of E. pisciphila H93 alleviated the deleterious effects of excessive HM supplements and promoted the growth of maize (roots and shoots) under HM stress conditions, though it significantly decreased the biomass of inoculated maize under no HM stress. Further analysis showed that the colonization of E. pisciphila H93 improved the tolerance of maize to HM by restricting the translocation of HM ions from roots to shoots. This study demonstrated that under higher HM stress, such a mutual symbiosis between E. pisciphila and its host (maize) may be an efficient strategy to survive in the stressful environments.

Genetic diversity of the endemic gourmet mushroom Thelephora ganbajun from south-western China

The ectomycorrhizal fungus Thelephora ganbajun is an endemic gourmet mushroom in Yunnan province, south-western China. However, despite its widespread consumer appeal, nutritional value and potential ecological role in natural forests, very little is known about its genetics, diversity and ecology. In this study, we investigated DNA sequence variation at the internal transcribed spacer (ITS) regions among 156 specimens collected from 23 sites of nine regions in Yunnan Province. Our analysis identified a total of 34 ITS haplotypes and these haplotypes were clustered into five distinct phylogenetic groups. The evolutionary divergences among these clades are similar to or greater than many known sister species pairs within the genus Thelephora and the closely related genus Tomentella. Among the 34 ITS haplotypes, 22 were represented by one specimen each and the remaining 12 were each shared by two or more specimens. The most common haplotype contained 68 specimens distributed in 21 of the 23 sites, a result consistent with gene flow among geographical populations. However, analysis of molecular variance (AMOVA) revealed low but significant genetic differentiation among local and regional populations. Interestingly, the Mantel test identified that the extent of genetic differentiation was not significantly correlated with geographical distance. Our study revealed significant genetic divergence within Th. ganbajun and limited but detectable gene flow among geographical populations of this endemic ectomycorrhizal gourmet mushroom.

Two new phenyl esters from Litsea euosma

Two new phenyl esters, named as euosmoside A (1) and euosmoside B (2), have been isolated from the leaves and twigs of Litsea euosma. Their structures were elucidated on the basis of spectroscopic methods.

Chromone glycosides from Knoxia corymbosa

Four new chromone glycosides, corymbosins K1-K4 (3–6), together with two known compounds, noreugenin (1) and undulatoside A (2), were isolated from the whole plant of Knoxia corymbosa (Rubiaceae). The structures of the new compounds were established through extensive NMR or X-ray spectroscopic analysis as 7-O-β-d-allopyranosyl-5-hydroxy-2-methylchromone (corymbosin K1, 3), 7-O-β-d-6-acetylglucopyranosyl-5-hydroxy-2-methylchromone (corymbosin K2, 4), 7-O-[6-O-(4-O-trans-caffeoyl-β-d-allopyranosyl)]-β-d-glucopyranosyl-5-hydroxy-2-methylchromone (corymbosin K3, 5) and 7-O-[6-O-(4-O-trans-feruloyl-β-d-allopyranosyl)]-β-d-glucopyranosyl-5-hydroxy-2- methylchromone (corymbosin K4, 6). Compounds 2–5 were subjected to test their immunomodulatory activity in vitro.