Stressed out symbiotes:hypotheses for the influence of abiotic stress on arbuscular mycorrhizal fungi

Abiotic stress is a widespread threat to both plant and soil communities. Arbuscular mycorrhizal (AM) fungi can alleviate effects of abiotic stress by improving host plant stress tolerance, but the direct effects of abiotic stress on AM fungi are less well understood. We propose two hypotheses predicting how AM fungi will respond to abiotic stress. The stress exclusion hypothesis predicts that AM fungal abundance and diversity will decrease with persistent abiotic stress. The mycorrhizal stress adaptation hypothesis predicts that AM fungi will evolve in response to abiotic stress to maintain their fitness. We conclude that abiotic stress can have effects on AM fungi independent of the effects on the host plant. AM fungal communities will change in composition in response to abiotic stress, which may mean the loss of important individual species. This could alter feedbacks to the plant community and beyond. AM fungi will adapt to abiotic stress independent of their host plant. The adaptation of AM fungi to abiotic stress should allow the maintenance of the plant-AM fungal mutualism in the face of changing climates. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00442-016-3673-7) contains supplementary material, which is available to authorized users

Unfair Advantages for Hepatocellular Carcinoma Patients Listed for Liver Transplant in Short‐Wait Regions Following 2015 Hepatocellular Carcinoma Policy Change

For patients with hepatocellular carcinoma (HCC) listed for liver transplantation (LT), United Network for Organ Sharing (UNOS) enacted policy changes in 2015 to improve equity between HCC and non-HCC patients. We evaluated the impact of these changes on regional disparities in wait-list dropout and LT. We included patients in the UNOS database listed with Model for End-Stage Liver Disease HCC exceptions in long-wait regions (LWRs), mid-wait regions (MWRs), and short-wait regions (SWRs) before these policy changes (era 1, January 1 to December 31, 2013) and after (era 2, October 7, 2015, to October 7, 2016). Cumulative incidence of wait-list dropout and LT were evaluated using competing risk regression. Median time to LT increased by 3.6 months (3.1 to 6.7 months) in SWRs and 1.3 months (6.9 to 8.2 months) in MWRs (P < 0.001), with a slight decrease in LWRs (13.4 to 12.9 months; P = 0.02). The 2-year cumulative incidence of dropout increased from 9.7% to 14.8% in SWRs (P = 0.03) and from 18.9% to 22.6% in MWRs (P = 0.18) but decreased in LWRs from 26.7% to 24.8% (P = 0.31). Factors predicting wait-list dropout included listing in era 2 (hazard ratio [HR], 1.17), in LWRs (HR, 2.56), and in MWRs (HR, 1.91). Regional differences in wait-list outcomes decreased with policy changes, but HCC patients in SWRs remain advantaged. Recent policy change may narrow these disparities

Allelic variation of the Beta-, gamma- and delta-kafirin genes in diverse Sorghum genotypes

The β-, γ- and δ-kafirin genes were sequenced from 35 Sorghum genotypes to investigate the allelic diversity of seed storage proteins. A range of grain sorghums, including inbred parents from internationally diverse breeding programs and landraces, and three wild Sorghum relatives were selected to encompass an extensive array of improved and unimproved germplasm in the Eusorghum. A single locus exists for each of the expressed kafirin-encoding genes, unlike the multigenic α-kafirins. Significant diversity was found for each locus, with the cysteine-rich β-kafirin having four alleles, including the first natural null mutant reported for this prolamin subfamily. This allele contains a frame shift insertion at +206 resulting in a premature stop codon. SDS-PAGE revealed that lines with this allele do not produce β-kafirin. An analysis of flour viscosity reveals that these β-kafirin null lines have a difference in grain quality, with significantly lower viscosity observed over the entire Rapid ViscoAnalyser time course. There was less diversity at the protein level within the cysteine-rich γ-kafirin, with only two alleles in the cultivated sorghums. There were only two alleles for the δ-kafirin locus among the S. bicolor germplasm, with one allele encoding ten extra amino acids, of which five were methionine residues, with an additional methionine resulting from a nucleotide substitution. This longer allele encodes a protein with 19.1% methionine. The Asian species, S. propinquum, had distinct alleles for all three kafirin genes. We found no evidence for selection on the three kafirin genes during sorghum domestication even though the δ-kafirin locus displayed comparatively low genetic variation. This study has identified genetic diversity in all single copy seed storage protein genes, including a null mutant for β-kafirin in Sorghum