1. Ectopic maltase alleviates dwarf phenotype and improves plant frost tolerance of maltose transporter mutants
- Author
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Ilka Haferkamp, Oliver Trentmann, Jelena Cvetkovic, Simona Eicke, Regina Rode, Samuel C. Zeeman, Michaela Fischer-Stettler, H. Ekkehard Neuhaus, Benjamin Pommerrenig, Isabel Keller, and Jacqueline Altensell
- Subjects
0106 biological sciences ,Regular Issue ,Physiology ,Saccharomyces cerevisiae ,Mutant ,Arabidopsis ,Plant Science ,01 natural sciences ,03 medical and health sciences ,chemistry.chemical_compound ,Genetics ,Arabidopsis thaliana ,030304 developmental biology ,0303 health sciences ,biology ,Arabidopsis Proteins ,Membrane Transport Proteins ,food and beverages ,Maltose ,biology.organism_classification ,Yeast ,Cell biology ,Cold Temperature ,Chloroplast ,Phenotype ,chemistry ,Maltase ,010606 plant biology & botany - Abstract
Maltose, the major product of starch breakdown in Arabidopsis (Arabidopsis thaliana) leaves, exits the chloroplast via the maltose exporter1 MEX1. Consequently, mex1 loss-of-function plants exhibit substantial maltose accumulation, a starch-excess phenotype and a specific chlorotic phenotype during leaf development. Here, we investigated whether the introduction of an alternative metabolic route could suppress the marked developmental defects typical for mex1 loss-of-function mutants. To this end, we ectopically expressed in mex1 chloroplasts a functional maltase (MAL) from baker’s yeast (Saccharomyces cerevisiae, chloroplastidial MAL [cpMAL] mutants). Remarkably, the stromal MAL activity substantially alleviates most phenotypic peculiarities typical for mex1 plants. However, the cpMAL lines contained only slightly less maltose than parental mex1 plants and their starch levels were, surprisingly, even higher. These findings point to a threshold level of maltose responsible for the marked developmental defects in mex1. While growth and flowering time were only slightly retarded, cpMAL lines exhibited a substantially improved frost tolerance, when compared to wild-types. In summary, these results demonstrate the possibility to bypass the MEX1 transporter, allow us to differentiate between possible starch-excess and maltose-excess responses, and demonstrate that stromal maltose accumulation prevents frost defects. The latter insight may be instrumental for the development of crop plants with improved frost tolerance.
- Published
- 2021