Photosynthetic acclimation to elevated CO2 in relation to Rubisco gene expression in three C3 species.

Wheat (Triticum aestivum L. var. DL 1266-5), sunflower (Helianthus annuus L. var. MSFH 17) and mungbean [Vigna radiata (L.) Wilczek var. P 9072] were grown in field under atmospheric (360 +/- 10 cm3 m(-3), AC) and elevated (650 +/- 50 cm3 m(-3), EC) CO2 concentrations in open top chambers for entire period of growth and development. Photosynthetic acclimation to elevated CO2 was examined by comparing photosynthesis rate (Pn), Pn/Ci curves, leaf contents of RuBP carboxylase/oxygenase (Rubisco), change in the transcripts of Rubisco small subunit (SSU) gene and leaf carbohydrate constituents in AC and EC grown plants. The study indicated that photosynthetic acclimation to elevated CO2 concentration in wheat occurred because of down regulation of Rubisco, through limitation imposed on Rubisco SSU gene expression, as a consequence of sugar accumulation in the leaves. Leaf starch accumulators, sunflower and mungbean, showed no down regulation of Pn under EC. The Rubisco contents (%) in leaf soluble protein and rbcS transcript levels were not significantly affected in EC plants compared to AC plants of sunflower and mungbean. The study indicated that accumulation of excess assimilates in the leaves as starch was less inhibitory to Pn and would, therefore, be an important trait for sustenance of Pn not only under EC, but also under AC, where Pn inhibited by end products.

A new measure to study phylogenetic relations in the brown algal order Ectocarpales: the "codon impact parameter".

We analyse forty-seven chloroplast genes of the large subunit of RuBisCO, from the algal order Ectocarpales, sourced from GenBank. Codon-usage weighted by the nucleotide base-bias defines our score called the codon-impact-parameter. This score is used to obtain phylogenetic relations amongst the 47 Ectocarpales. We compare our classification with the ones done earlier.