Establishment of reference (housekeeping) genes via quantitative real-time PCR for investigation of the genomic basis of abiotic stress resistance in Psammochloa villosa (Poaceae).

Psammochloa villosa is a desert plant growing in Northwest China with considerable resistance to abiotic stress, including drought, cold, and salt. To facilitate future studies of stress resistance in Psammochloa villosa, we sought to establish a suite of reference (or housekeeping) genes for utilization within future gene expression studies. Specifically, we selected nine candidate genes based on prior studies and new transcriptomic data for P. villosa, and we evaluated their expression stability in three different tissues of P. villosa under different treatments simulating abiotic stress conditions using four different bioinformatics assessments. Our results showed that TIP41 (TIP41-like family protein) was the most stable reference gene in drought- and salt-stressed leaves and salt-stressed stems, ELF-1α (elongation factor 1-α) was the most stable in cold-stressed leaves and drought- and salt-stressed roots, ACT (actin) was the most stable in drought-stressed stems, TUA (α-tubulin) was the most stable in cold-stressed stems, and 18S rRNA (18S ribosomal RNA) was the most stable in cold-stressed roots. Additionally, we tested the utility of these candidate reference genes to detect the expression pattern of P5CS (Δ1-pyrroline-5-carboxylate synthetase), which is a drought-related gene. This study is the first report on selecting and validating reference genes of P. villosa under various stress conditions and will benefit future investigations of the genomic mechanisms of stress resistance in this ecologically important species.

[Carbon and nitrogen stable isotopes technology in the researches on alpine meadow ecosystem in Qinghai-Tibet Plateau: Progress and prospect]. / ç¢³æ°®ç¨³å®šåŒä½ç´ æŠ€æœ¯åœ¨é’è—é«˜åŽŸé«˜å¯’è‰ç”¸ç”Ÿæ€ç³»ç»Ÿç ”ç©¶ä¸­çš„åº”ç”¨: 进展与展望.

Carbon and nitrogen stable isotopic technique has been widely used in research of glassland ecosystems. Here, we summarized studies using carbon and nitrogen stable isotopes in the alpine meadow ecosystem on the Qinghai-Tibet Plateau. Firstly, we reviewed the environmental factors which influenced carbon and nitrogen isotope composition (δ13C and δ15N) of plants and soils in alpine meadow, such as altitude, moisture, fertilization, grassland degradation, and temperature. The values of plant δ13C were positively correlated with altitude, and negatively correlated with atmospheric pressure, grassland degradation and temperature. The relationship between plant δ13C and precipitation was non-linear. The values of soil δ13C were positively correlated with altitude and grassland degradation. The values of plant δ15N were positively correlated with soil moisture and fertilization, and negatively correlated with grassland degradation. Secondly, we reviewed the current application and progresses of 13C and 15N in the identification of plant photosynthetic type, water use, nutrient transport along food chain and carbon and nitrogen cycle in the alpine meadow. Finally, we prospected the 13C and 15N isotopes application in researches on soil organic carbon and soil respiration in the alpine meadow, transitions of vegetation type, and climate change, soil N2O trace, exploration of vegetation degradation, identification of the origin of Tibetan medicine and animal food, etc. 13C and 15N isotopes could be widely used and play important roles in researches on the alpine ecosystems.

Nutrient-induced shifts of dominant species reduce ecosystem stability via increases in species synchrony and population variability.

The mechanisms underlying nutrient-induced diversity-stability relationships have been examined extensively. However, the effects of nutrient-induced shifts of dominant species on ecosystem stability have rarely been evaluated. We compiled a dataset from a long-term nitrogen (N) and phosphorus (P) enrichment experiment conducted in an alpine grassland on the Tibetan Plateau to test the effects of nutrient-induced shifts of dominant species on stability. Our results show that N enrichment increased synchrony among the dominant species, which contributed to a significant increase in synchrony of the whole community. Meanwhile, N-induced shifts in dominant species composition significantly increased population variability. Increases in species synchrony and population variability resulted in a decline in ecosystem stability. Our study has important implications for progress in understanding the role of plant functional compensation in the stability of ecosystem functions, which is critical for better understanding the mechanisms driving both community assembly and ecosystem functions.