Tsamir-Rimon Mor, Ben-Dor Shifra, Feldmesser Ester, Oppenhimer-Shaanan Yaara, David-Schwartz Rakefet, Samach Alon, Klein Tamir
Plant & Environmental Sciences Department, Weizmann Institute of Science, Rehovot, 76100, Israel.
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, 76100, Israel.
New Phytol. 2021 Feb;229(3):1398-1414. doi: 10.1111/nph.16907. Epub 2020 Oct 1.
Carbon reserve use is a major drought response in trees, enabling tree survival in conditions prohibiting photosynthesis. However, regulation of starch metabolism under drought at the whole-tree scale is still poorly understood. To this end, we combined measurements of nonstructural carbohydrates (NSCs), tree physiology and gene expression. The experiment was conducted outside on olive trees in pots under 90 d of seasonal spring to summer warming. Half of the trees were also subjected to limited water conditions for 28 d. Photosynthesis decreased in dehydrating trees from 19 to 0.5 µmol m s during the drought period. Starch degradation and mannitol production were a major drought response, with mannitol increasing to 71% and 41% out of total NSCs in shoots and roots, respectively. We identified the gene family members potentially relevant either to long-term or stress-induced carbon storage. Partitioning of expression patterns among β amylase and starch synthase family members was observed, with three β amylases possibly facilitating the rapid starch degradation under heat and drought. Our results suggest a group of stress-related, starch metabolism genes, correlated with NSC fluctuations during drought and recovery. The daily starch metabolism gene expression was different from the stress-mode starch metabolism pattern, where some genes are uniquely expressed during the stress-mode response.
碳储备利用是树木应对干旱的主要方式，能使树木在禁止光合作用的条件下存活。然而，在全树尺度下干旱对淀粉代谢的调控仍知之甚少。为此，我们结合了对非结构性碳水化合物（NSCs）、树木生理学和基因表达的测量。实验在室外盆栽橄榄树上进行，经历了从春季到夏季90天的季节性升温。其中一半树木还经历了28天的水分受限条件。在干旱期间，脱水树木的光合作用从19微摩尔·米⁻²·秒⁻¹降至0.5微摩尔·米⁻²·秒⁻¹。淀粉降解和甘露醇产生是主要的干旱响应，甘露醇分别占地上部和根部总NSCs的71%和41%。我们鉴定出了可能与长期或胁迫诱导的碳储存相关的基因家族成员。观察到β淀粉酶和淀粉合酶家族成员之间表达模式的划分，其中三种β淀粉酶可能促进了高温和干旱下淀粉的快速降解。我们的数据表明，一组与胁迫相关的淀粉代谢基因，与干旱及恢复期间NSCs的波动相关。每日淀粉代谢基因表达不同于胁迫模式下的淀粉代谢模式，在胁迫模式响应期间一些基因独特表达。
