International Maize and Wheat Improvement Center (CIMMYT), El Batan, Mexico.
Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
J Exp Bot. 2022 Sep 12;73(16):5745-5757. doi: 10.1093/jxb/erac218.
Water deficit currently acts as one of the largest limiting factors for agricultural productivity worldwide. Additionally, limitation by water scarcity is projected to continue in the future with the further onset of effects of global climate change. As a result, it is critical to develop or breed for crops that have increased water use efficiency and that are more capable of coping with water scarce conditions. However, increased intrinsic water use efficiency (iWUE) typically brings a trade-off with CO2 assimilation as all gas exchange is mediated by stomata, through which CO2 enters the leaf while water vapor exits. Previously, promising results were shown using guard-cell-targeted overexpression of hexokinase to increase iWUE without incurring a penalty in photosynthetic rates or biomass production. Here, two homozygous transgenic tobacco (Nicotiana tabacum) lines expressing Arabidopsis Hexokinase 1 (AtHXK1) constitutively (35SHXK2 and 35SHXK5) and a line that had guard-cell-targeted overexpression of AtHXK1 (GCHXK2) were evaluated relative to wild type for traits related to photosynthesis and yield. In this study, iWUE was significantly higher in GCHXK2 compared with wild type without negatively impacting CO2 assimilation, although results were dependent upon leaf age and proximity of precipitation event to gas exchange measurement.
目前，水分亏缺是全球农业生产力的最大限制因素之一。此外，随着全球气候变化影响的进一步加剧，未来水资源短缺的情况预计将持续下去。因此，开发或培育具有更高水分利用效率、更能适应缺水条件的作物至关重要。然而，内在水分利用效率（iWUE）的提高通常会带来与 CO2 同化的权衡，因为所有气体交换都由保卫细胞介导，CO2 通过保卫细胞进入叶片，而水蒸气则从保卫细胞逸出。以前，通过靶向保卫细胞过表达己糖激酶来提高 iWUE 而不降低光合速率或生物量生产的方法，已经取得了有希望的结果。在这里，我们评估了两个组成型表达拟南芥己糖激酶 1（AtHXK1）的纯合转基因烟草（Nicotiana tabacum）株系（35SHXK2 和 35SHXK5）和一个具有保卫细胞靶向过表达 AtHXK1 的株系（GCHXK2）相对于野生型在与光合作用和产量相关的性状上的表现。在这项研究中，与野生型相比，GCHXK2 的 iWUE 显著提高，而 CO2 同化不受负面影响，尽管结果取决于叶片年龄和降水事件与气体交换测量的接近程度。
