Journal Article

Application of HB17, an <i>Arabidopsis</i> class II homeodomain-leucine zipper transcription factor, to regulate chloroplast number and photosynthetic capacity

Graham J. Hymus, Suqin Cai, Elizabeth A. Kohl, Hans E. Holtan, Colleen M. Marion, Shiv Tiwari, Don R. Maszle, Marjorie R. Lundgren, Melissa C. Hong, Namitha Channa, Paul Loida, Rebecca Thompson, J. Philip Taylor, Elena Rice, Peter P. Repetti, Oliver J. Ratcliffe, T. Lynne Reuber and Robert A. Creelman

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 64, issue 14, pages 4479-4490
Published in print November 2013 | ISSN: 0022-0957
Published online September 2013 | e-ISSN: 1460-2431 | DOI: https://dx.doi.org/10.1093/jxb/ert261

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Transcription factors are proposed as suitable targets for the control of traits such as yield or food quality in plants. This study reports the results of a functional genomics research effort that identified ATHB17, a transcription factor from the homeodomain-leucine zipper class II family, as a novel target for the enhancement of photosynthetic capacity. It was shown that ATHB17 is expressed natively in the root quiescent centre (QC) from Arabidopsis embryos and seedlings. Analysis of the functional composition of genes differentially expressed in the QC from a knockout mutant (athb17-1) compared with its wild-type sibling revealed the over-representation of genes involved in auxin stimulus, embryo development, axis polarity specification, and plastid-related processes. While no other phenotypes were observed in athb17-1 plants, overexpression of ATHB17 produced a number of phenotypes in Arabidopsis including enhanced chlorophyll content. Image analysis of isolated mesophyll cells of 35S::ATHB17 lines revealed an increase in the number of chloroplasts per unit cell size, which is probably due to an increase in the number of proplastids per meristematic cell. Leaf physiological measurements provided evidence of improved photosynthetic capacity in 35S::ATHB17 lines on a per unit leaf area basis. Estimates of the capacity for ribulose-1,5-bisphosphate-saturated and -limited photosynthesis were significantly higher in 35S::ATHB17 lines.

Keywords: Chloroplast number; chloroplast size; homeodomain-leucine zipper; leaf development; photosynthetic capacity; transcription factor.

Journal Article.  7458 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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