Quantitative proteomics study on Lsi1 in regulation of rice (Oryza sativa L.) cold resistance

Abstract

Low temperature is one of the major abiotic stresses which severely affects the productivity and the geographical distribution of rice (Oryza sativa). Silicon is considered a broad spectrum alleviator to combat stress in rice plant. Rice root absorbs silicon by a silicon transporter, Low silicon gene 1 (Lsi1). To gain a better understanding of cold stress responses triggered by overexpression of Lsi1 in rice (Oryza sativa L.), we carried out physiological and molecular studies between Lsi1-overexpression Dular (Lsi1-D) and its wild type (WD). Two leaf stage rice seedlings of above mentioned both lines were treated at 15 °C/12 °C (day/night) for 7 days. WD seedling leaves were turned comparatively yellow as compared to Lsi1-D seedlings. Microscopic studies showed significantly more deposition of silicon bodies in epidermal cells of Lsi1-D leaf seedlings in comparison with WD leaves. Lsi1-D leaves comparatively, depicted more SOD, POD and CAT activity, chlorophyll a, b contents in consistency with more silicon concentration. Protein extraction was carried out from whole seedling of both lines and further analyzed by tandem mass tag quantitative proteomics approach with double replicates. Among 393 reproducible proteins, 63 were up-regulated and 39 proteins were down-regulated. The total cold responsive differential proteins were involved in several processes, i.e. photosynthesis, signal transduction, redox homeostasis, hormone metabolism, carbohydrate metabolism, cell wall organization, N-assimilation, protein processing and secondary metabolism. We confirmed up-regulation of key proteins involved in cold-responsive pathway at mRNA level through qPCR such as chlorophyll a–b binding protein 1, peroxidase 2, signaling G-proteins RIC1, aquaporin PIP1.2, 1, 4-alpha-glucan branching enzyme, germin-like protein subfamily 2 member 4 and germin-like protein subfamily 8 member 2. In conclusion, our study provides new insights into cold stress responses in rice seedlings triggered by Lsi1-overexpression defense pathway.