IC4R003-lncRNA-2015-26734039

Project Title

RNA-Seq Analysis of Rice Roots Reveals the Involvement of Post-Transcriptional Regulation in Response to Cadmium Stress

The Background of This Project

• Cadmium (Cd) is one of the most toxic heavy metals to organisms. Unlike some essential heavy metals, such as copper (Cu), zinc (Zn), manganese (Mn), and nickel (Ni) that are necessary for plant growth and development, Cd is considered a non-essential metal element for plants. Widely spread Cd pollution has significantly affected human health both in term so fits direct effect on crop production and its high accumulation in the edible part of crops such as rice. Previous studies have shown that excessive Cd in plants causes an accumulation of reactive oxygen species (ROS), lipid peroxidation, enzyme inactivation, and DNA and membrane damage, resulting in various toxicity phenotypes, such as chlorosis, wilting, growth reduction, and cell death. However,assignalingmolecules,ROS can be produced at controlled levels and can lead to tolerance responses.
• Plants have evolved several common mechanisms to prevent excess Cd effects, such as extracellular exudates, transport, chelation, and sequestration and repair of damaged proteins. By inhibiting toxic metal transport,plants can reduce to xic metal influx and enhanc emetal removal from the cytosol. Several transporters involved in the acquisition, distribution and home ostasis of Cd in plants have been identified, including heavy metal ATPases (HMA), ATP-binding cassette transporters (ABC), natural resistance-associated macrophage protein (Nramp), metal transporter proteins (MTPs), and low-affinity cation transporter (LCT). One recent study showed that Cd enter into rice root through OsNramp5, originally uptake transporter for essential element Mn, because of the unspecificity properties of this transporter. The HMAf amily transporter Os HMA2 and Os HMA3 playsroles in translocation of Cd into shoot and sequestration of Cd into vacuole,respectively. In mature stage, OsLCT1 regulates cadmium transport into rice grains. In Arabidopsis, the ABC transporter AtPDR8 is a cadmium extrusion pump conferring heavy metal resistance, whereas the phytochelatin transporters AtABCC1 and AtABCC2 mediate tolerance to cadmium and mercury. Cadmium-inducible expression of the ABC-type transporter AtABCC3 increases phytochelatin-mediated cadmium tolerance in Arabidopsis. Glutathione (GSH) and phytochelatins (PCs) chelating represent another detoxification strategy in plant cells.

Plant Culture & Treatment

• Rice (Oryza sativa spp. japonica cv. Nipponbare) seeds were sown on mesh floating in a 0.5mM calcium chloride (CaCl 2 ) solution and maintained for 2 days at 25–30 ◦ C in the dark, thereby inducing germination. Seedlings were transferred into Kimura B nutrient solution containing the macronutrients (mM): (NH 4 ) 2 SO 4 (0.18), MgSO 4 ·7H 2 O (0.27), KNO 3 (0.09), Ca(NO 3 ) 2 ·4H 2 O (0.18), and KH 2 PO 4 (0.09); and the micronutrients (µM): MnCl 2 ·4H 2 O (0.5), H 3 BO 3 (3), (NH 4 ) 6 Mo 7 O 24 ·4H 2 O (1), ZnSO 4 ·7H 2 O (0.4), Fe-EDTA (20), and 0.2µM CuSO 4 ·5H 2 O. The pH of the nutrient solution was adjusted to 5.5, and held under normal greenhouse conditions with illumination provided by cool-white fluorescent lamps. Growth conditions were as follows: 27/24 ◦ C day/night temperatures, 60–80% relative humidity, and a 14/10-h day/night photoperiod. Fifteen-day-old rice seedlings were treated with or without 10 and 100µM solutions of Cd (II) hydrochloride (CdCl 2 ) for 24h. Following Cd treatment, roots were harvested for RNA extraction and subsequent analysis. Samples were stored at −80 ◦ C if not immediately used for RNA isolation. All experiments were performed at least twice with three biological replicates each, and representative results of one experiment are shown.

Figure 1 Box plots for relative phenotypic values. The median of each trait is shown as the horizontal bar in the box, and the upper and lower sides of a box represent the first and third quartile values of the distribution, respectively. Whiskers extended to 1.5 times the interquartile range (box size) or to the maximum/minimum values.

Research Findings

Table 1 Effect of ozone stress on phenotypic values

Corresponding Author

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