Journal Article

Senescence-induced ectopic expression of the <i>A. tumefaciens ipt</i> gene in wheat delays leaf senescence, increases cytokinin content, nitrate influx, and nitrate reductase activity, but does not affect grain yield

Blanka Sýkorová, Gabriela Kurešová, Sasha Daskalova, Marie Trčková, Klára Hoyerová, Ivana Raimanová, Václav Motyka, Alena Trávníčková, Malcolm C. Elliott and Miroslav Kamínek

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 2, pages 377-387
Published in print February 2008 | ISSN: 0022-0957
Published online February 2008 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/erm319

Show Summary Details

Preview

The manipulation of cytokinin levels by senescence-regulated expression of the Agrobacterium tumefaciens ipt gene through its control by the Arabidopsis SAG12 (senescence-associated gene 12) promoter is an efficient tool for the prolongation of leaf photosynthetic activity which potentially can affect plant productivity. In the present study, the efficiency of this approach was tested on wheat (Triticum aestivum L.)—a monocarpic plant characterized by a fast switch from vegetative to reproductive growth, and rapid translocation of metabolites from leaves to developing grains after anthesis. When compared with the wild-type (WT) control plants, the SAG12::ipt wheat plants exhibited delayed chlorophyll degradation only when grown under limited nitrogen (N) supply. Ten days after anthesis the content of chlorophyll and bioactive cytokinins of the first (flag) leaf of the transgenic plants was 32% and 65% higher, respectively, than that of the control. There was a progressive increase in nitrate influx and nitrate reductase activity. However, the SAG12::ipt and the WT plants did not show differences in yield-related parameters including number of grains and grain weight. These results suggest that the delay of leaf senescence in wheat also delays the translocation of metabolites from leaves to developing grains, as indicated by higher accumulation of (15N-labelled) N in spikes of control compared with transgenic plants prior to anthesis. This delay interferes with the wheat reproductive strategy that is based on a fast programmed translocation of metabolites from the senescing leaves to the reproductive sinks shortly after anthesis.

Keywords: Cytokinins; grain yield; ipt gene; nitrate; nitrate reductase; SAG12 promoter; senescence; wheat

Journal Article.  6387 words.  Illustrated.

Subjects: Plant Sciences and Forestry

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.