BSc - MSc (Int.)

The present programme entitled “Effect of elevated CO2 on iron transporter gene
expression and iron dynamics in rice (Oryza sativa L.)” was carried out in the Department
of Plant Biotechnology and Department of Plant Physiology, College of Agriculture,
Vellayani, during the year 2021-2022 with the objective of evaluating the effect eCO2
condition on expression of iron transporter genes OsIRT1 and OsIRT2 and mechanism of
iron transport in rice. By using in-silico methods, additional characteristics of the two
proteins were investigated
The experiment was laid out in CRD with two treatments and 15 replications. Plants
were maintained under open field condition (390 ppm) and under the elevated CO2 of
500ppm in the Open Top Chamber (OTC) facility at the Department of Plant Physiology.
The extent of variation in growth, physiological, and biochemical parameters as well as
parameters related to Fe dynamics were assessed in rice variety Uma (MO16). The
expression analyses of two genes were done using real time PCR.
In the present study, larger numbers of tillers, productive tillers, dry matter buildup,
root weight, and straw production were seen under 500 ppm CO2 exposure than under open
field conditions. OTC condition resulted in higher total chlorophyll content, photosynthetic
rate, and total reducing sugars while the rate of transpiration, stomatal conductance, and
total soluble protein content decreased in the plants grown inside OTC. Physiological and
biochemical parameters were recorded at the active tillering stage. The shoot, root, and
grains of plants maintained in both environments were examined for parameters linked to
iron dynamics. Additionally, soil samples from the two experimental settings were taken,
and their Fe status was examined. The dry matter accumulation, number of tillers, number
productive tillers and root weight increased significantly when grown inside the OTC with
eCO2. The grain yield and straw yield increased by 59.4% and 36.2% respectively upon
exposure to eCO2 compared to control plants which were grown in open field.
Photosynthetic parameters like chlorophyll content and photosynthetic rate were found
significantly increased under eCO2 condition leading to significantly higher total reducing
sugar content at active tillering stage. The stomatal conductance, transpiration rate and total
soluble protein content were reduced by eCO2 at the active tillering stage.
The iron transporter genes, OsIRT1 and OsIRT2 were down regulated under eCO2
condition. Iron content in roots, straw and grains of eCO2 exposed plants were reduced by
10.3%, 24.5% and 37.5% respectively. The physicochemical analyses (Expasy protparam)
of the proteins OsIRT1 and OsIRT2 revealed that they contain 374 and 370 amino acids
respectively.
The instability indices of OsIRT1 and OsIRT2 proteins were 41 and 45 respectively
indicating that both these proteins are unstable. The phylogenetic analysis of OsIRT1 using
MEGA X showed maximum similarity with IRT1-like protein Panicum hallii. OsIRT2 had
maximum similarity with IRT1-like protein Hordeum vulgare subsp. vulgare. The Fe metal
ion binding sites on OsIRT1 and OsIRT2 were projected to have a total of 21 amino acid
residues and 24 amino acid residues respectively (MIB tool). Bioinformatics tools were
used to predict the physicochemical parameters (Expsay protparam, secondary structure
(PSIPRED v 2.0), and 3D homology structure (iTASSER) which was validated using
Ramachanadran plot. In silico predictions done on Metal binding site, docking (MIB) and
visualization (Pymol) revealed the characteristics of iron binding sites of these proteins.
Elevated CO2 levels had a positive impact on the overall growth and yield
performance of the rice variety Uma by improving the radiation interception and
photosynthetic efficiency, but had an adverse effect on grain quality with reduced iron
content. This can be due to modified absorption, translocation and remobilization pattern of
Fe under eCO2 condition and the down-regulation of the Fe transporter genes OsIRT1
and OsIRT2 by eCO2. The predictions on the properties of the proteins OsIRT1 and
OsIRT2 done through in silico means could be usedas a foundation for future research on
their role in regulating the levels of micronutrients in crop plants. The influence of eCO2 on
morphological, physiological, and molecular factors in rice could be utilised for developing
climate change mitigation strategies.