Miyoshi Yuta, Soma Fumiyuki, Yin Yong-Gen, Suzui Nobuo, Noda Yusaku, Enomoto Kazuyuki, Nagao Yuto, Yamaguchi Mitsutaka, Kawachi Naoki, Yoshida Eiji, Tashima Hideaki, Yamaya Taiga, Kuya Noriyuki, Teramoto Shota, Uga Yusaku
Takasaki Advanced Radiation Research Institute, National Institutes for Quantum Science and Technology (QST), Takasaki, Japan.
Institute of Crop Science, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan.
Front Plant Sci. 2023 Jan 18;13:1024144. doi: 10.3389/fpls.2022.1024144. eCollection 2022.
Rice is susceptible to abiotic stresses such as drought stress. To enhance drought resistance, elucidating the mechanisms by which rice plants adapt to intermittent drought stress that may occur in the field is an important requirement. Roots are directly exposed to changes in the soil water condition, and their responses to these environmental changes are driven by photosynthates. To visualize the distribution of photosynthates in the root system of rice plants under drought stress and recovery from drought stress, we combined X-ray computed tomography (CT) with open type positron emission tomography (OpenPET) and positron-emitting tracer imaging system (PETIS) with C tracer. The short half-life of C (20.39 min) allowed us to perform multiple experiments using the same plant, and thus photosynthate translocation was visualized as the same plant was subjected to drought stress and then re-irrigation for recovery. The results revealed that when soil is drier, C-photosynthates mainly translocated to the seminal roots, likely to promote elongation of the root with the aim of accessing water stored in the lower soil layers. The photosynthates translocation to seminal roots immediately stopped after rewatering then increased significantly in crown roots. We suggest that when rice plant experiencing drought is re-irrigated from the bottom of pot, the destination of C-photosynthates translocation immediately switches from seminal root to crown roots. We reveal that rice roots are responsive to changes in soil water conditions and that rice plants differentially adapts the dynamics of photosynthates translocation to crown roots and seminal roots depending on soil conditions.
水稻易受干旱胁迫等非生物胁迫的影响。为了增强抗旱性，阐明水稻植株适应田间可能出现的间歇性干旱胁迫的机制是一项重要需求。根系直接暴露于土壤水分条件的变化中，其对这些环境变化的反应由光合产物驱动。为了可视化干旱胁迫下及从干旱胁迫恢复过程中水稻植株根系系统中光合产物的分布，我们将X射线计算机断层扫描（CT）与开放式正电子发射断层扫描（OpenPET）以及带有碳示踪剂的正电子发射示踪成像系统（PETIS）相结合。碳的短半衰期（20.39分钟）使我们能够对同一植株进行多次实验，因此在同一植株遭受干旱胁迫然后再灌溉恢复的过程中，光合产物的转运得以可视化。结果表明，当土壤较干燥时，碳光合产物主要转运至胚根，可能是为了促进根系伸长以获取储存在土壤下层的水分。重新浇水后，光合产物向胚根的转运立即停止，然后在冠根中显著增加。我们认为，当遭受干旱的水稻植株从花盆底部重新灌溉时，碳光合产物转运的目的地会立即从胚根切换至冠根。我们揭示了水稻根系对土壤水分条件的变化有反应，并且水稻植株根据土壤条件差异地调整光合产物向冠根和胚根转运的动态过程。
