Effects of Elevated CO2 on Levels of Primary Metabolites and Transcripts of Genes Encoding Respiratory Enzymes and Their Diurnal Patterns in Arabidopsis thaliana: Possible Relationships with Respiratory Rates

Abstract

Elevated CO2 affects plant growth and photosynthesis, which results in changes in plant respiration. However, the mechanisms underlying the responses of plant respiration to elevated CO2 are poorly understood. In this study, we measured diurnal changes in the transcript levels of genes encoding respiratory enzymes, the maximal activities of the enzymes and primary metabolite levels in shoots of Arabidopsis thaliana grown under moderate or elevated CO2 conditions (390 or 780 parts per million by volume CO2, respectively). We examined the relationships between these changes and respiratory rates. Under elevated CO2, the transcript levels of several genes encoding respiratory enzymes increased at the end of the light period, but these increases did not result in changes in the maximal activities of the corresponding enzymes. The levels of some primary metabolites such as starch and sugar phosphates increased under elevated CO2, particularly at the end of the light period. The O2 uptake rate at the end of the dark period was higher under elevated CO2 than under moderate CO2, but higher under moderate CO2 than under elevated CO2 at the end of the light period. These results indicate that the changes in O2 uptake rates are not directly related to changes in maximal enzyme activities and primary metabolite levels. Instead, elevated CO2 may affect anabolic processes that consume respiratory ATP, thereby affecting O2 uptake rates.

Variation in Leaf Respiration Rates at Night Correlates with Carbohydrate and Amino Acid Supply

“…Therefore, major amino acids could display a strong correlation with R N as a result of the sensitivity of their pool size to changes in both C and N assimilation. As total free amino acids accumulate during the light period and are depleted during the night period in Arabidopsis and tobacco (Nicotiana tabacum; Fritz et al, 2006;Gibon et al, 2006;Watanabe et al, 2014), amino acid levels in the early night, not unlike starch, could be an indicator of the previous day's aggregate metabolic activity (Fig. 7).…”

Examining plant physiological responses to climate change through an evolutionary lens

“…For example, many pollinators prefer larger flowers, although increased frequency or severity of drought may impose selection for smaller flowers that reduce water loss (Galen, 2000). Elevated [CO 2 ] alters the nutritional quality of nectar rewards through direct effects on photosynthesis and sugar production (Watanabe et al, 2014). Increases in [CO 2 ] over the past 170 years also reduced pollen protein concentration in Solidago canadensis (Ziska et al, 2016).…”

Suppression of Chloroplastic Alkenal/One Oxidoreductase Represses the Carbon Catabolic Pathway in Arabidopsis Leaves during Night

“…For this analysis, mRNA was extracted from the leaves of both wild-type and aor-1 plants at three different times: at the end of the day (1 h before the night period started), at midnight (4 h after the night period started), and at the end of the night (7 h after the night period started). As an internal standard, we used Rps15aA (Watanabe et al, 2014), and the mRNA level in the wild type at the end of the day was set to 1 (Fig. 4).…”

“…For the evaluation of PEPC, CSY, ACO, and PDH activities, leaf protein was extracted in buffer (50 mM KH 2 PO 4 -K 2 HPO 4 [pH 7.6], 10 mM MgSO 4 , 1 mM EDTA, 5 mM DTT, 0.05% [v/v] Triton X-100, 5% [w/v] polyvinylpyrrolidone, and one protein cocktail tablet [Roche]), as described by Watanabe et al (2014), and leaf protein solution was obtained by centrifugation (15,000g, 2 min, and 4°C).…”