Enhancement of Salinity Tolerance during Rice Seed Germination by Presoaking with Hemoglobin

Sheng Xu,Ziyi He,Fei Ma,Jianfei Feng,Bing Hu,Wenbiao Shen,Jie Yang

doi:10.3390/ijms12042488

Abstract

Salinity stress is an important environmental constraint limiting the productivity of many crops worldwide. In this report, experiments were conducted to investigate the effects of seed presoaking by bovine hemoglobin, an inducer of heme oxygenase-1 (HO-1), on salinity tolerance in rice (Oryza sativa) plants. The results showed that different concentrations of the hemoglobin (0.01, 0.05, 0.2, 1.0, and 5.0 g/L) differentially alleviated the inhibition of rice seed germination and thereafter seedling shoot growth caused by 100 mM NaCl stress, and the responses of 1.0 g/L hemoglobin was the most obvious. Further analyses showed that application of hemoglobin not only increased the HO-1 gene expression, but also differentially induced catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) activities or transcripts, thus decreasing the lipid peroxidation in germinating rice seeds subjected to salt stress. Compared with non-hemoglobin treatment, hemoglobin presoaking also increased the potassium (K) to sodium (Na) ratio both in the root and shoot parts after salinity stress. The effect is specific for HO-1 since the potent HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX) blocked the positive actions of hemoglobin on seed germination and seedling shoot growth. Overall, these results suggested that hemoglobin performs an advantageous role in enhancement of salinity tolerance during rice seed germination.

Highlights

Seed germination is a complex process involving various physical and biochemical cues such as water, light and phytohormones
A growing body of evidence showed that the inhibitory effect of salt stress on seed germination is alleviated by phytohormones, including ethylene [1], cytokinin (CTK) [2]), gibberellin acid (GA) [3], and messenger molecules such as hydrogen peroxide (H2O2) [4], nitric oxide (NO) [5], and carbon monoxide (CO) [6]
Further results showed that the different concentrations of hemoglobin pretreatment were able to reverse the negative impact of NaCl on seed germination and shoot growth inhibition, with a maximal response at 1.0 g/L

Summary

Introduction

Seed germination is a complex process involving various physical and biochemical cues such as water, light and phytohormones. A growing body of evidence showed that the inhibitory effect of salt stress on seed germination is alleviated by phytohormones, including ethylene [1], cytokinin (CTK) [2]), gibberellin acid (GA) [3], and messenger molecules such as hydrogen peroxide (H2O2) [4], nitric oxide (NO) [5], and carbon monoxide (CO) [6]. Secondary stresses often occur, such as oxidative stress due to the overproduction of reactive oxygen species (ROS) in salt stressed plants [7]. To quench ROS, plant cells possess both enzymatic and non-enzymatic mechanisms for the scavenging of ROS overproduction. It has been well established that the coordination activities of the multiple forms of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) in the different cell compartments, achieve a balance between the rate of formation and the scavenging of ROS, and maintain ROS at suitable levels required for cell signaling

Results

Discussion

Conclusion