Kinase POGSK-3ß modulates fungal plant polysaccharide-degrading enzyme production and development.

The filamentous fungus Penicillium oxalicum secretes integrative plant polysaccharide-degrading enzymes (PPDEs) applicable to biotechnology. Glycogen synthase kinase-3ß (GSK-3ß) mediates various cellular processes in eukaryotic cells, but the regulatory mechanisms of PPDE biosynthesis in filamentous fungi remain poorly understood. In this study, POGSK-3ß (POX_c04478), a homolog of GSK-3ß in P. oxalicum, was characterised using biochemical, microbiological and omics approaches. Knockdown of POGSK-3ß in P. oxalicum using a copper-responsive promoter replacement system led to 53.5 - 63.6%, 79.0 - 92.8% and 76.8 - 94.7% decreases in the production of filter paper cellulase, soluble starch-degrading enzyme and raw starch-degrading enzyme, respectively, compared with the parental strain ΔKu70. POGSK-3ß promoted mycelial growth and conidiation. Transcriptomic profiling and real-time quantitative reverse transcription PCR analyses revealed that POGSK-3ß dynamically regulated the expression of genes encoding major PPDEs, as well as fungal development-associated genes. The results broadened our understanding of the regulatory functions of GKS-3ß and provided a promising target for genetic engineering to improve PPDE production in filamentous fungi. KEY POINTS: • The roles of glycogen synthase kinase-3ß were investigated in P. oxalicum. • POGSK-3ß regulated PPDE production, mycelial growth and conidiation. • POGSK-3ß controlled the expression of major PPDE genes and regulatory genes.

[Partitioning ecosystem respiration of a Platycladus orientalis forest in the west mountainous area of Beijing, China using stable carbon isotope].

Based on stable carbon isotope, we quantitatively partitioned ecosystem respiration in a Platycladus orientalis forest in the west mountainous area of Beijing. Results from this study could lay the foundation for carbon exchange research in forest ecosystems of this region. The spectroscopy technique was used to continuously measure CO2 concentrations and δ13C values at different height of the forest. Soil and branch chambers were used for measuring nighttime δ13C values in underground and aboveground respiration, and then the proportions of respiration components were calculated. Combined with soil respiration efflux measurement, ecosystem respiration was then quantitatively partitioned. The results showed that δ13C values of respiratory components fluctuated, which ranged from -31.74‰ to -23.33‰ in aboveground respiration of plants and from -32.11‰ to -27.74‰ in soil respiration. The δ13C values of ecosystem respiration was at the middle of those ranges. Soil respiration averaged 1.70 µmol·m-2·s-1 at night, accounting for 47%-91% of ecosystem respiration. Aboveground respiration averaged 0.72 µmol·m-2·s-1, contributing less to ecosystem respiration. Daytime respiration based on isotope mixing model calculation had greater variability than that based on temperature response model, with a mean value of 2.31 µmol·m-2·s-1 and 2.28 µmol·m-2·s-1, respectively.

[Tree-ring δ13C and water use efficiency of Platycladus orientalis in mountains of Beijing]. / åŸºäºŽæ ‘è½®Î´13C的北京山区侧柏水分利用效率.

Water use efficiency (WUE) is different among species and regions. Few literatures have been reviewed related to long-term WUE of Platycladus orientalis in mountainous areas of Beijing, China. Tree-ring δ13C of P. orientalis was used to determine the long-term variation of annual intrinsic water use efficiency (WUEi) and its response to environmental change. Combining with quantification of tree-ring width, the relationship between net carbon sequestration and WUEi of P. orientalis was eventually explored. The results showed that mean annual temperature increased with the increase of time from 1918 to 2013, whereas annual precipitation fiercely fluctuated. Tree-ring δ13C decreased and WUEi increased over time. WUEi was positively related and more sensitive to air temperature increasing than temperature decreasing. Correlation between WUEi and fluctuated annualprecipitation was ambiguous, which indicated the precipitation was not the main factor affecting WUEi. The de-trend tree-ring width of P. orientalis increased initially and then decreased, especially in recent 20 years. According to the correlation between WUEi and environmental factors, temperature resulted in stomatal conductance (gs) decreasing, which caused a reduction in evapotranspiration and an increase in respiratory loss, leading to the increase of WUEi and a down trend in net carbon sequestration and tree growth.

[Water source of typical plants in rocky mountain area of Beijing, China]. / åŒ—äº¬åœŸçŸ³å±±åŒºå ¸åž‹æ¤ç‰©æ°´åˆ†æ¥æº.

Water is the key factor limiting plant growth in seasonal arid area. In order to analyze the water sources of community plant (Platycladus orientalis, Vitex negundo var. heterophylla, Broussonetia papyrifera and Lespedeza bicolor) in Beijing mountainous area, we measured hydrogen and oxygen stable isotope ratio (δD and δ18O) values of their xylem water and potential water sources. The results showed the four species had different water sources. P. orientalis mainly absorbed water from 40-60, 60-80 and 80-100 cm soil layers, and the utilization ratio of the three layers was 23.3%-25.9%. It still grabbed water from 0-20 and 20-40 cm soil layers with the utilization ratio of 12.3% and 13.0%, respectively. V. negundo var. heterophylla mainly absorbed 60-80 and 80-100 cm depth soil water, and the utilization rate was 51.9% and 25.2%, respectively, while it barely absorbed water in other soil layers. B. papyrifera mainly absorbed 0-20 and 20-40 cm depth soil water, and the utilization rate was 47.5% and 36.8%, respectively. L. bicolor used the water from five layers, and the utilization ratio of 0-20, 20-40 and 40-60 cm layer was 21.4%-22.8%, and that of 60-80 and 80-100 cm layer was 15.2%-18.3%, respectively. The competition was higher in mixed forest of P. orientalis and L. bicolor because they had similar water sources. It was better to mix V. negundo var. heterophylla and B. papyrifera because their water sources were complementary. The results could provide reference for the best combination of plant species to restore the damaged ecological environment.

[A review of water and carbon flux partitioning and coupling in SPAC using stable isotope techniques]. / åŸºäºŽç¨³å®šåŒä½ç´ çš„SPACæ°´ç¢³æ‹†åˆ†åŠè€¦åˆç ”ç©¶è¿›å±•.

Soil-vegetation-atmosphere continuum (SPAC) is one of the important research objects in the field of terrestrial hydrology, ecology and global change. The process of water and carbon cycling, and their coupling mechanism are frontier issues. With characteristics of tracing, integration and indication, stable isotope techniques contribute to the estimation of the relationship between carbon sequestration and water consumption in ecosystems. In this review, based on a brief introduction of stable isotope principles and techniques, the applications of stable isotope techniques to water and carbon exchange in SPAC using optical stable isotope techniques were mainly explained, including: partitioning of net carbon exchange into photosynthesis and respiration; partitioning of evapotranspiration into transpiration and evaporation; coupling of water and carbon cycle at the ecosystem scale. Advanced techniques and methods provided long-term and high frequency measurements for isotope signals at the ecosystem scale, but the issues about the precision and accuracy for measurements, partitioning of ecosystem respiration, adaptability for models under non-steady state, scaling up, coupling mechanism of water and carbon cycles, were challenging. The main existing research findings, limitations and future research prospects were discussed, which might help new research and technology development in the field of stable isotope ecology.

[Foliar water use efficiency of Platycladus orientalis sapling under different soil water contents]. / ä¸åŒåœŸå£¤å«æ°´é‡ä¸‹ä¾§æŸå¹¼æ ‘å¶ç‰‡æ°´åˆ†åˆ©ç”¨æ•ˆçŽ‡.

The determination of plant foliar water use efficiency will be of great value to improve our understanding about mechanism of plant water consumption and provide important basis of regional forest ecosystem management and maintenance, thus, laboratory controlled experiments were carried out to obtain Platycladus orientalis sapling foliar water use efficiency under five different soil water contents, including instantaneous water use efficiency (WUEgs) derived from gas exchange and short-term water use efficiency (WUEcp) caculated using carbon isotope model. The results showed that, controlled by stomatal conductance (gs), foliar net photosynthesis rate (Pn) and transpiration rate (Tr) increased as soil water content increased, which both reached maximum va-lues at soil water content of 70%-80% field capacity (FC), while WUEgs reached a maximum of 7.26 mmol·m-2·s-1 at the lowest soil water content (35%-45% FC). Both δ13C of water-soluble leaf and twig phloem material achieved maximum values at the lowest soil water content (35%-45% FC). Besides, δ13C values of leaf water-soluble compounds were significantly greater than that of phloem exudates, indicating that there was depletion in 13C in twig phloem compared with leaf water-soluble compounds and no obvious fractionation in the process of water-soluble material transportation from leaf to twig. Foliar WUEcp also reached a maximum of 7.26 mmol·m-2·s-1 at the lowest soil water content (35%-45% FC). There was some difference between foliar WUEgs and WUEcp under the same condition, and the average difference was 0.52 mmol·m-2·s-1. The WUEgs had great space-time variability, by contrast, WUEcp was more representative. It was concluded that P. orientalis sapling adapted to drought condition by increasing water use efficiency and decreasing physiological activity.

[Variations and determinants of CO2 concentration and δ13C in Platycladus orientalis plantation in Beijing mountainous area, China]. / åŒ—äº¬å±±åŒºä¾§æŸäººå·¥æž—å† CO2æµ“åº¦åŠå ¶Î´13Cå€¼å˜åŒ–ç‰¹å¾å’Œå½±å“å› å­.

This research employed off-axis integrated cavity output spectroscopy technique to observe CO2 concentration and δ13C values of planted Platycladus orientalis in Beijing mountainous area. We compared the variation between CO2 concentration and δ13C values in the plantation at different heights observed by every 0.5 h to explore how the CO2 concentration and δ13C values responded to the meteorological factors. The results showed that the CO2 concentration showed the pattern of "first decreased and then increased" after sunrise. The lowest value (352.5 µmol·mol-1) appeared at 16:00-16:30, while the maximum value (402.0 µmol·mol-1) was observed at about 5:00. However, the change of δ13C value was not significant and regular, which increased firstly and then decreased in the surface layer while opposite for the canopy. Atmospheric CO2 concentration decreased with the increasing height. In the height of 0, 2, 5, 8, 12.5 and 18 m, the average daily value was 386.5, 369.9, 368.2, 367.8, 367.9 and 367.9 µmol·mol-1, respectively. In contrast, the δ13C values tended to rise correspondingly with height with the average daily value being -16.0‰, -13.7‰, -13.5‰, -13.5‰, -13.1‰ and -13.3% at 0, 2, 5, 8, 12.5 and 18 m, respectively. The stepwise regression analysis showed that temperature and humidity were the main factors for the changes of atmospheric CO2 concentration and δ13C values. The saturated vapor pressure difference (VPD) affected the concentration of CO2 in the forest and wind speed could affect it on the canopy. However, soil moisture, soil electric conductivity and net solar radiation affected the CO2 concentration and δ13C values in surface layer. All these environmental factors influenced CO2 concentration and δ13C values through their influences on the photosynthesis and respiration.