The value of mutants unable to carry out photorespiration

Abstract

Manipulation of the CO2 concentration of the atmosphere allows the selection of photorespiratory mutants from populations of seeds treated with powerful mutagens such as sodium azide. So far, barley lines deficient in activity of phosphoglycolate phosphatase, catalase, the glycine to serine conversion, glutamine synthetase, glutamate synthase, 2-oxoglutarate uptake and serine: glyoxylate aminotransferase have been isolated. In addition one line of pea lacking glutamate synthase activity and one barley line containing reduced levels of Rubisco are available. The characteristics of these mutations are described and compared with similar mutants isolated from populations of Arabidopsis. As yet, no mutant lacking glutamine synthetase activity has been isolated from Arabidopsis and possible reasons for this difference between barley and Arabidopsis are discussed. The value of these mutant plants in the elucidation of the mechanism of photorespiration and its relationships with CO2 fixation and amino acid metabolism are highlighted.

Comprehensive Dissection of Spatiotemporal Metabolic Shifts in Primary, Secondary, and Lipid Metabolism during Developmental Senescence in Arabidopsis

“…However, a direct support for this hypothesis in the context of our results is currently lacking. That said, a relationship between senescence and photorespiration has been suggested in several studies of photorespirationdeficient mutants (Somerville, 1986;Blackwell et al, 1988;Leegood et al, 1995). However, differences in light conditions (long days in the whole-plant experiment and short days in the single-leaf experiment) for plant growth are another possible explanation for the differences in Gly and Ser levels observed here.…”

d-GLYCERATE 3-KINASE, the Last Unknown Enzyme in the Photorespiratory Cycle in Arabidopsis, Belongs to a Novel Kinase Family

“…The seedlings die within approximately 2 weeks, unless being transferred to CO 2 -enriched air ( Figure 5A). Such behavior has been observed with most but not all photorespiratory mutants (Somerville and Ogren, 1979;Somerville, 1984Somerville, , 2001Blackwell et al, 1988;Richter et al, 2005) and confirms the essential role of GLYK for the proper functioning of the photorespiratory C 2 cycle already in very early stages of Arabidopsis development. Under the low-photorespiratory conditions of elevated CO 2 (1200 mL L ÿ1 ), homozygous Atglyk1-1 and Atglyk1-2 plants show reduced growth in comparison with wild-type plants, but they are fully viable and fertile.…”

A Cytosolic Pathway for the Conversion of Hydroxypyruvate to Glycerate during Photorespiration in Arabidopsis

“…This is evident from the lethality of both chemical and T-DNA insertion mutations in the AGT1 gene in combination with the normalization of the mutants observed under elevated CO 2 (Somerville and Ogren, 1980;Liepman and Olsen, 2001). Both effects are typical features of photorespiratory mutants (Blackwell et al, 1988;Somerville, 2001;Boldt et al, 2005;Voll et al, 2006;Schwarte and Bauwe, 2007).…”