Abstract
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−2 s−1 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.
Original language | American English |
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Pages (from-to) | 1398-1414 |
Number of pages | 17 |
Journal | New Phytologist |
Volume | 229 |
Issue number | 3 |
DOIs | |
State | Published - Feb 2021 |
Bibliographical note
Funding Information:The authors thank the Merle S. Cahn Foundation; the Monroe and Marjorie Burk Fund for Alternative Energy Studies; Mr and Mrs Norman Reiser; the Weizmann Center for New Scientists; the estate of Helen Nichunsky; the Benoziyo Endowment Fund for the Advancement of Science; and the Edith & Nathan Goldberg Career Development Chair. MT is grateful for the support of the Women’s League of Israel, with scholarships provided during her MSc research. The authors declare no competing interest in the preparation of this manuscript.
Funding Information:
The authors are grateful to S. Wolf and N. Glanz (Hebrew University), for the HPLC analysis; to G. Ben-Ari (ARO Volcani Center) for sharing the database of the olive genome and for commenting on an earlier version of the manuscript, together with J. Gruenzweig (Hebrew University); and to the members of the Klein laboratory (Weizmann TreeLab) for helpful discussions and comments. Five anonymous referees are acknowledged for providing useful comments, which improved the article. The authors thank the Merle S. Cahn Foundation; the Monroe and Marjorie Burk Fund for Alternative Energy Studies; Mr and Mrs Norman Reiser; the Weizmann Center for New Scientists; the estate of Helen Nichunsky; the Benoziyo Endowment Fund for the Advancement of Science; and the Edith & Nathan Goldberg Career Development Chair. MT is grateful for the support of the Women?s League of Israel, with scholarships provided during her MSc research. The authors declare no competing interest in the preparation of this manuscript.
Publisher Copyright:
© 2020 The Authors New Phytologist © 2020 New Phytologist Trust
Keywords
- carbon source
- drought response
- drought tolerance
- mannitol
- starch degradation
- starch synthesis