Unidad de Genómica Avanzada/LANGEBIO, Centro de Investigación y de Estudios Avanzados, Irapuato, México.
Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA.
J Exp Bot. 2022 Aug 11;73(14):4716-4732. doi: 10.1093/jxb/erac188.
Soil mechanical impedance precludes root penetration, confining root system development to shallow soil horizons where mobile nutrients are scarce. Using a two-phase-agar system, we characterized Arabidopsis responses to low and high mechanical impedance at three root penetration stages. We found that seedlings whose roots fail to penetrate agar barriers show a significant reduction in leaf area, root length, and elongation zone and an increment in root diameter, while those capable of penetrating show only minor morphological effects. Analyses using different auxin-responsive reporter lines, exogenous auxins, and inhibitor treatments suggest that auxin responsiveness and PIN-mediated auxin distribution play an important role in regulating root responses to mechanical impedance. The assessment of 21 Arabidopsis accessions revealed that primary root penetrability varies widely among accessions. To search for quantitative trait loci (QTLs) associated to root system penetrability, we evaluated a recombinant inbred population derived from Landsberg erecta (Ler-0, with a high primary root penetrability) and Shahdara (Sha, with a low primary root penetrability) accessions. QTL analysis revealed a major-effect QTL localized in chromosome 3, ROOT PENETRATION INDEX 3 (q-RPI3), which accounted for 29.98% (logarithm of odds=8.82) of the total phenotypic variation. Employing an introgression line (IL-321) with a homozygous q-RPI3 region from Sha in the Ler-0 genetic background, we demonstrated that q-RPI3 plays a crucial role in root penetrability. This multiscale study reveals new insights into root plasticity during the penetration process in hard agar layers, natural variation, and genetic architecture behind primary root penetrability in Arabidopsis.
土壤力学阻抗阻碍根系穿透，将根系系统的发展局限于浅层土壤中，那里移动的养分稀缺。我们使用双相琼脂系统，在三个根系穿透阶段表征了拟南芥对低和高机械阻抗的反应。我们发现，未能穿透琼脂障碍的幼苗叶片面积、根长和伸长区显著减少，而根直径增加，而能够穿透的幼苗仅表现出轻微的形态效应。使用不同的生长素响应报告基因系、外源生长素和抑制剂处理的分析表明，生长素响应和 PIN 介导的生长素分布在调节根系对机械阻抗的反应中起着重要作用。对 21 个拟南芥品系的评估表明，主根穿透性在品系之间差异很大。为了寻找与根系穿透性相关的数量性状基因座 (QTL)，我们评估了来自 Landsberg erecta (Ler-0，具有较高的主根穿透性)和 Shahdara (Sha，具有较低的主根穿透性)品系的重组自交系群体。QTL 分析揭示了一个位于染色体 3 上的主效 QTL，ROOT PENETRATION INDEX 3 (q-RPI3)，它解释了总表型变异的 29.98%（对数优势=8.82）。利用具有 Sha 中 q-RPI3 区域的纯合子的导入系 (IL-321)在 Ler-0 遗传背景下，我们证明 q-RPI3 在根穿透性中起着关键作用。这项多尺度研究揭示了在硬琼脂层中穿透过程中根系可塑性、自然变异以及拟南芥主根穿透性的遗传结构的新见解。
