Journal Article

Uptake and allocation of carbon and nitrogen in <i>Vicia narbonensis</i> plants with increased seed sink strength achieved by seed-specific expression of an amino acid permease

Klaus-Peter Götz, Nicole Staroske, Ruslana Radchuk, R. J. Neil Emery, Klaus-Dieter Wutzke, Helmut Herzog and Hans Weber

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 12, pages 3183-3195
Published in print September 2007 | ISSN: 0022-0957
Published online August 2007 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/erm164

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Over-expressing an amino acid permease in Vicia narbonensis seeds increases sink strength for N that is evident from the higher seed protein content and seed weight. Here, the effect of increased seed sink strength of line AAP-12 on growth, development, and on whole plant carbon and nitrogen uptake and partitioning is analysed. AAP-12 plants have a prolonged growth period. Accumulation and partitioning of dry matter and N in leaves, stems, and pods are higher whereas remobilization to the seeds is delayed, indicating that the switch from growth to reserve allocation and remobilization is delayed. Measuring uptake and allocation of 15N-ammonia applied via the roots revealed a higher and longer label uptake period during maturation. Measuring whole plant carbon fixation and allocation after 13C labelling shows higher levels at maturation, particularly in seeds, indicating higher seed sink strength for C and increased allocation into maturing seeds. Levels of cytokinins were dramatically increased in AAP-12 seeds indicating its role in nitrogen-mediated growth stimulation. AAP-12 seeds have higher natural abundances for 13C indicating increased C fixation via PEP carboxylase in order to meet the higher demand of carbon acceptors for amino acid synthesis. In summary, increased seed sink strength for N in AAP-12 stimulates seed growth, but also that of vegetative organs, which finally leads to a higher ratio of vegetative to seed biomass at maturity and thus a lower harvest index. Therefore, the increased N uptake due to higher seed demand of AAP-12 is partly compensated by growth stimulation of vegetative organs.

Keywords: Amino acid permease; C and N partitioning; cytokinin; harvest index; legume seed development; seed sink strength; transgenic plants

Journal Article.  7577 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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