Department of Biochemistry and Microbiology, Institute of Biology, Warsaw University of Life Sciences-SGGW, 02-776 Warsaw, Poland.
Biopolymer Analytics, Institute of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24-25 Building 20, 14476 Potsdam-Golm, Germany.
Int J Mol Sci. 2021 Jul 4;22(13):7203. doi: 10.3390/ijms22137203.
Plants are often challenged by an array of unfavorable environmental conditions. During cold exposure, many changes occur that include, for example, the stabilization of cell membranes, alterations in gene expression and enzyme activities, as well as the accumulation of metabolites. In the presented study, the carbohydrate metabolism was analyzed in the very early response of plants to a low temperature (2 °C) in the leaves of 5-week-old potato plants of the Russet Burbank cultivar during the first 12 h of cold treatment (2 h dark and 10 h light). First, some plant stress indicators were examined and it was shown that short-term cold exposure did not significantly affect the relative water content and chlorophyll content (only after 12 h), but caused an increase in malondialdehyde concentration and a decrease in the expression of , a homolog of the NADH dehydrogenase gene. In addition, it was shown that the content of transitory starch increased transiently in the very early phase of the plant response (3-6 h) to cold treatment, and then its decrease was observed after 12 h. In contrast, soluble sugars such as glucose and fructose were significantly increased only at the end of the light period, where a decrease in sucrose content was observed. The availability of the monosaccharides at constitutively high levels, regardless of the temperature, may delay the response to cold, involving amylolytic starch degradation in chloroplasts. The decrease in starch content, observed in leaves after 12 h of cold exposure, was preceded by a dramatic increase in the transcript levels of the key enzymes of starch degradation initiation, the α-glucan, water dikinase (GWD-EC 2.7.9.4) and the phosphoglucan, water dikinase (PWD-EC 2.7.9.5). The gene expression of both dikinases peaked at 9 h of cold exposure, as analyzed by real-time PCR. Moreover, enhanced activities of the acid invertase as well as of both glucan phosphorylases during exposure to a chilling temperature were observed. However, it was also noticed that during the light phase, there was a general increase in glucan phosphorylase activities for both control and cold-stressed plants irrespective of the temperature. In conclusion, a short-term cold treatment alters the carbohydrate metabolism in the leaves of potato, which leads to an increase in the content of soluble sugars.
植物经常受到各种不利环境条件的挑战。在低温下，许多变化会发生，例如，细胞膜的稳定、基因表达和酶活性的改变，以及代谢物的积累。在本研究中，在低温（2°C）下，对 5 周龄的 Russet Burbank 品种马铃薯叶片中植物的早期响应进行了碳水化合物代谢分析，在冷处理的前 12 小时（黑暗 2 小时和光照 10 小时）。首先，检查了一些植物应激指标，结果表明，短期低温处理不会显著影响相对含水量和叶绿素含量（仅在 12 小时后），但会导致丙二醛浓度增加， 和 NADH 脱氢酶基因的同源物的表达减少。此外，结果表明，在植物对冷处理的早期（3-6 小时）响应中，暂态淀粉的含量短暂增加，然后在 12 小时后观察到其减少。相比之下，葡萄糖和果糖等可溶糖仅在光照期结束时显著增加，同时观察到蔗糖含量下降。无论温度如何，单糖的含量都保持在较高水平，这可能会延迟涉及叶绿体中淀粉分解的冷反应。在低温处理 12 小时后，叶片中淀粉含量的减少先于淀粉降解起始关键酶的转录水平急剧增加，即 α-葡聚糖、水二激酶（GWD-EC 2.7.9.4）和磷酸葡聚糖、水二激酶（PWD-EC 2.7.9.5）。通过实时 PCR 分析，在冷暴露 9 小时时，两种二激酶的基因表达均达到峰值。此外，在低温处理过程中，酸性转化酶以及两种葡聚糖磷酸化酶的活性增强。然而，还注意到，在光照阶段，无论温度如何，对照和冷胁迫植物的葡聚糖磷酸化酶活性普遍增加。总之，短期低温处理会改变马铃薯叶片中的碳水化合物代谢，导致可溶糖含量增加。
