Rico-Cambron Thelma Y, Bello-Bello Elohim, Martínez Octavio, Herrera-Estrella Luis
National Laboratory of Genomics for Biodiversity (LANGEBIO), Unit of Advanced Genomics, CINVESTAV, Irapuato, Guanajuato, 36824, Mexico.
Plant Molecular and Cellular Biology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA.
Plant Methods. 2023 Nov 15;19(1):127. doi: 10.1186/s13007-023-01107-w.
Survival rate (SR) is frequently used to compare drought tolerance among plant genotypes. While a variety of techniques for evaluating the stress status of plants under drought stress conditions have been developed, determining the critical point for the recovery irrigation to evaluate plant SR often relies directly on a qualitative inspection by the researcher or on the employment of complex and invasive techniques that invalidate the subsequent use of the tested individuals.
Here, we present a simple, instantaneous, and non-invasive method to estimate the survival probability of Arabidopsis thaliana plants after severe drought treatments. The quantum yield (QY), or efficiency of photosystem II, was monitored in darkness (Fv/Fm) and light (Fv'/Fm') conditions in the last phase of the drought treatment before recovery irrigation. We found a high correlation between a plant's Fv'/Fm' value before recovery irrigation and its survival phenotype seven days after, allowing us to establish a threshold between alive and dead plants in a calibration stage. This correlation was maintained in the Arabidopsis accessions Col-0, Ler-0, C24, and Kondara under the same conditions. Fv'/Fm' was then applied as a survival predictor to compare the drought tolerance of transgenic lines overexpressing the transcription factors ATAF1 and PLATZ1 with the Col-0 control.
The results obtained in this work demonstrate that the chlorophyll a fluorescence parameter Fv'/Fm' can be used as a survival predictor that gives a numerical estimate of the Arabidopsis drought SR before recovery irrigation. The procedure employed to get the Fv'/Fm' measurements is fast, non-destructive, and requires inexpensive and easy-to-handle equipment. Fv'/Fm' as a survival predictor can be used to offer an overview of the photosynthetic state of the tested plants and determine more accurately the best timing for rewatering to assess the SR, especially when the symptoms of severe dehydration between genotypes are not contrasting enough to identify a difference visually.
存活率（SR）常被用于比较植物基因型间的耐旱性。虽然已开发出多种评估干旱胁迫条件下植物胁迫状态的技术，但确定恢复灌溉以评估植物存活率的临界点通常直接依赖于研究人员的定性检查，或采用复杂且有侵入性的技术，而这些技术会使后续对受试个体的使用无效。
在此，我们提出一种简单、即时且非侵入性的方法来估计拟南芥植株在严重干旱处理后的存活概率。在恢复灌溉前干旱处理的最后阶段，于黑暗（Fv/Fm）和光照（Fv'/Fm'）条件下监测光系统II的量子产率（QY），即效率。我们发现恢复灌溉前植株的Fv'/Fm'值与其七天后的存活表型之间存在高度相关性，这使我们能够在校准阶段确定存活与死亡植株之间的阈值。在相同条件下，这种相关性在拟南芥生态型Col - 0、Ler - 0、C24和Kondara中得以维持。随后，Fv'/Fm'被用作存活预测指标，以比较过表达转录因子ATAF1和PLATZ1的转基因株系与Col - 0对照的耐旱性。
本研究所得结果表明，叶绿素a荧光参数Fv'/Fm'可作为存活预测指标，在恢复灌溉前对拟南芥干旱存活率给出数值估计。获取Fv'/Fm'测量值所采用的程序快速、无损，且所需设备廉价且易于操作。Fv'/Fm'作为存活预测指标可用于概述受试植物的光合状态，并更准确地确定再浇水以评估存活率的最佳时机，尤其是当基因型间严重脱水症状差异不够明显以至于无法通过视觉识别差异时。
