DataSheet3_Root-based inorganic carbon uptake increases the growth of Arabidopsis thaliana and changes transporter expression and nitrogen and sulfur metabolism.pdf

Root-based uptake of inorganic carbon has been suggested as an additional carbon source. Our study aimed to characterize and understand the root-based uptake and fixation mechanisms and their impact on plant growth. 13C-labeled bicarbonate fed to Arabidopsis roots was assimilated into aspartic acid but mainly into sucrose, indicating that the added inorganic carbon was transported to the leaves. A hydroponic treatment was also established for A. thaliana using 2 mM NaHCO3 at pH 5.6, which enhanced the photosynthetic and growth parameters. According to transcriptome sequencing data, the observed enhancement in growth may be orchestrated by trehalose-6-phosphate signaling and supported by augmented nitrogen and sulfur assimilation. The analysis also revealed regulatory and transporter activities, including several nitrate (NRT2.1), and sulfate transporter (SULTR1;1 and SULTR1;2) candidates that could participate in bicarbonate uptake. Different transporters and carbon fixation mutants were assessed. Arabidopsis homologs of SLOW-TYPE ANION CHANNEL 1 (slah3) CARBONIC ANHYDRASE (βca4), and SULFATE TRANSPORTER (sultr1;2) mutants were shown to be inferior to the bicarbonate-treated wild types in several growth and root ultrastructural parameters. Besides, aquaporin genes PIP1;3 and PIP2;6 could play a negative role in the carbon uptake by venting carbon dioxide out of the plant. The findings support the hypothesis that the inorganic carbon is taken up by the root anion channels, mostly transported up to the shoots by the xylem, and fixed there by RuBisCo after the conversion to CO2 by carbonic anhydrases. The process boosts photosynthesis and growth by providing an extra carbon supply.

基于根系的无机碳吸收被认为是一种额外的碳源。本研究旨在解析并阐明基于根系的碳吸收与固定机制，及其对植物生长的影响。向拟南芥（Arabidopsis）根系施加13C标记的碳酸氢盐后，该无机碳被同化为天冬氨酸，且主要被同化为蔗糖，表明所添加的无机碳被转运至叶片。本研究还建立了拟南芥（Arabidopsis thaliana）的水培处理体系，采用pH 5.6的2 mM碳酸氢钠溶液，该处理可提升植株的光合与生长参数。转录组测序数据显示，观测到的生长促进效应可能由海藻糖-6-磷酸信号通路调控，并通过增强的氮与硫同化作用得以支撑。分析还揭示了一系列调控与转运活性相关的候选基因，包括数种硝酸盐转运蛋白（NRT2.1）以及硫酸盐转运蛋白（SULTR1;1和SULTR1;2），这些蛋白可能参与碳酸氢盐的吸收过程。研究对不同的转运蛋白与碳固定突变体进行了评估。结果显示，慢型阴离子通道1（SLOW-TYPE ANION CHANNEL 1, slah3）、碳酸酐酶（βca4）以及硫酸盐转运蛋白（sultr1;2）的拟南芥同源突变体，在多项生长与根系超微结构参数上均劣于经碳酸氢盐处理的野生型植株。此外，水通道蛋白基因PIP1;3与PIP2;6可能通过将二氧化碳排出植物体外，在碳吸收过程中发挥负调控作用。本研究结果支持如下假说：无机碳通过根系阴离子通道被吸收，主要经由木质部转运至地上部分，并在碳酸酐酶将其转化为二氧化碳后，由核酮糖-1,5-二磷酸羧化酶/加氧酶（RuBisCo）完成固定。该过程通过提供额外的碳源，促进了光合作用与植株生长。