会议号：腾讯会议 263 727 712
Biogeochemical processes in dynamic redox systems: challenges and novel approaches
摘要：动态的氧化还原条件（例如稻田、潮湿的热带土壤）显著影响氧化还原敏感的生物地球化学过程，进而通过大量氧化还原和生化过程影响土壤中重要元素如磷（P）和碳（C）的循环。然而，揭示稻田等缺氧条件下的生物地球化学过程及其机制仍然具有挑战性，因为氧化还原电位的时空变异性、水稻根系在根际释放氧气以及存在众多即使在没有氧气的情况下也能保持高氧化还原电位的可替代性电子受体。而且，大多数用于研究生物地球化学循环的方法都是在有氧条件下开发的。为了填补当前方法中的这一关键空白，开发了缺氧原位酶谱技术来定量和可视化土壤-根界面处的酶活性。我们也开发了一种在低氧化还原条件下的新型原位 32P/33P 荧光成像技术，用于监测和量化水稻根系对磷的吸收。这些创新性的成像技术能够定性和定量地记录根系原位发育的动态，并有助于揭示根际过程的潜在机制。
The changing redox conditions (e.g. rice paddies, humid tropical soils) significantly influence redox-sensitive biogeochemical processes, which in turn affect the cycling of important elements such as phosphorus (P) and carbon (C) in the soils by a multitude of redox, chemical, and biological processes. However, it is still challenging to uncover biogeochemical processes and mechanisms under anoxic conditions like paddy soils due to (1) the temporal and (micro)spatial variability in redox potential, (2) the diffusive release of oxygen (O2) by rice roots in the rhizosphere, and (3) the presence of alternative electron acceptors that maintain high redox potentials even in the absence of O2. Moreover, most approaches applied for studying biogeochemical cycles are developed under oxic conditions. To fill this key gap in current methods, the anoxic in-situ zymography was developed to map enzyme activities at soil-root interface. We developed a novel in-situ 32P/33P phosphor-imaging approach under low-redox conditions to monitor and quantify P uptake by rice roots derived from both inorganic and organic P sources. Such innovative imaging methodologies enable to qualitatively and quantitatively document the dynamics of the in-situ development of root systems and could help to uncover underlying mechanisms of rhizosphere processes.
The relationship between starch reserves and aspen growth
Starch is the main carbon storage in plants. Starch is important for the growth of herb Arabidopsis, but the role of starch in woody species is unknown. We generated starch defect hybrid aspen (Populus tremula x tremuloides) trees using CRISPR/Cas9 gene editing of the two PHOSPHOGLUCOMUTASE (PGM) genes coding for plastidial PGM isoforms essential for starch biosynthesis. We demonstrate that the absence of starch does not reduce tree growth even in short days showing that starch is not a critical carbon reserve during diel growth of aspen. The starch defect trees assimilated ~30% less CO2 compared to wild type under a range of irradiance levels but this did not reduce growth or wood density. This observation implied that tree growth is not limited by carbon assimilation under benign growth conditions. Moreover, the timing of bud set and bud flush in the starch defect trees was not altered implying that starch reserves are not critical for the seasonal growth-dormancy cycle. The findings are consistent with a passive starch storage mechanism that contrast with the annual Arabidopsis, and indicate that the capacity of the aspen trees to absorb CO2 is limited by the strength of sink tissue.