Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
Department of Computational and Systems Biology, John Innes Centre, Norwich, United Kingdom.
Elife. 2017 Sep 5;6:e27038. doi: 10.7554/eLife.27038.
Nutrient uptake by roots often involves substrate-dependent regulated nutrient transporters. For robust uptake, the system requires a regulatory circuit within cells and a collective, coordinated behaviour across the tissue. A paradigm for such systems is boron uptake, known for its directional transport and homeostasis, as boron is essential for plant growth but toxic at high concentrations. In , boron uptake occurs via diffusion facilitators (NIPs) and exporters (BORs), each presenting distinct polarity. Intriguingly, although boron soil concentrations are homogenous and stable, both transporters manifest strikingly swift boron-dependent regulation. Through mathematical modelling, we demonstrate that slower regulation of these transporters leads to physiologically detrimental oscillatory behaviour. Cells become periodically exposed to potentially cytotoxic boron levels, and nutrient throughput to the xylem becomes hampered. We conclude that, while maintaining homeostasis, swift transporter regulation within a polarised tissue context is critical to prevent intrinsic traffic-jam like behaviour of nutrient flow.
根系对养分的吸收通常涉及底物依赖性调节养分转运体。为了实现稳健的吸收，该系统需要细胞内的调节回路和组织内的集体协调行为。硼的吸收就是此类系统的典范，硼的吸收具有方向性和稳态性，因为硼是植物生长所必需的，但在高浓度下又具有毒性。在这种情况下，硼的吸收是通过扩散促进剂（NIPs）和外排蛋白（BORs）进行的，它们各自呈现出不同的极性。有趣的是，尽管土壤中的硼浓度是均匀且稳定的，但这两种转运蛋白都表现出明显的快速硼依赖性调节。通过数学建模，我们证明了这些转运蛋白的缓慢调节会导致生理上有害的振荡行为。细胞会周期性地暴露在潜在的细胞毒性硼水平下，养分向木质部的输送也会受到阻碍。我们得出的结论是，在维持稳态的同时，在极化组织环境中快速调节转运蛋白对于防止养分流动的内在交通堵塞样行为至关重要。
