Identification of Rice Genes Associated With Enhanced Cold Tolerance by Comparative Transcriptome Analysis With Two Transgenic Rice Plants Overexpressing DaCBF4 or DaCBF7, Isolated From Antarctic Flowering Plant Deschampsia antarctica.

Mi Young Byun,Woo Taek Kim,Hyoungseok Lee,Jungeun Lee,Hyun Park,Li Hua Cui,Andosung Lee

doi:10.3389/fpls.2018.00601

Abstract

Few plant species can survive in Antarctica, the harshest environment for living organisms. Deschampsia antarctica is the only natural grass species to have adapted to and colonized the maritime Antarctic. To investigate the molecular mechanism of the Antarctic adaptation of this plant, we identified and characterized D. antarctica C-repeat binding factor 4 (DaCBF4), which belongs to monocot CBF group IV. The transcript level of DaCBF4 in D. antarctica was markedly increased by cold and dehydration stress. To assess the roles of DaCBF4 in plants, we generated a DaCBF4-overexpressing transgenic rice plant (Ubi:DaCBF4) and analyzed its abiotic stress response phenotype. Ubi:DaCBF4 displayed enhanced tolerance to cold stress without growth retardation under any condition compared to wild-type plants. Because the cold-specific phenotype of Ubi:DaCBF4 was similar to that of Ubi:DaCBF7 (Byun et al., 2015), we screened for the genes responsible for the improved cold tolerance in rice by selecting differentially regulated genes in both transgenic rice lines. By comparative transcriptome analysis using RNA-seq, we identified 9 and 15 genes under normal and cold-stress conditions, respectively, as putative downstream targets of the two D. antarctica CBFs. Overall, our results suggest that Antarctic hairgrass DaCBF4 mediates the cold-stress response of transgenic rice plants by adjusting the expression levels of a set of stress-responsive genes in transgenic rice plants. Moreover, selected downstream target genes will be useful for genetic engineering to enhance the cold tolerance of cereal plants, including rice.

Highlights

Plants are sessile organisms and are constantly exposed to adverse environmental conditions, to which they have adapted (Lata and Prasad, 2011; Claeys and Inzé, 2013)
As the overexpression of barley HvCBF4 and wheat TaCBF14 increased the cold-stress tolerance of transgenic rice and barley plants, respectively (Oh et al, 2007; Soltész et al, 2013), we cloned the D. antarctica cDNA sequence encoding the C repeat (CRT)-dehydrationresponsive element-binding protein (DREB)-binding factor protein based on its sequence homology with HvCBF4 (Lee et al, 2013b)
Because the DaCBF4-overexpressing plants showed a coldspecific phenotype similar to that of the DaCBF7-overexpressing plants, we identified the genes responsible for the increased the cold tolerance by screening for genes up- or down-regulated in both transgenic rice plants

Summary

Introduction

Plants are sessile organisms and are constantly exposed to adverse environmental conditions, to which they have adapted (Lata and Prasad, 2011; Claeys and Inzé, 2013). (Poaceae) is one of two flowering plants that naturally inhabit Antarctica (Alberdi et al, 2002). This species has developed various adaptive mechanisms to survive in the Antarctic. The adaptations that enable D. antarctica to survive in the harsh environment of the maritime Antarctic include changes in the leaf anatomy and the physiology of the photosynthetic apparatus (Giełwanowska et al, 2005; Sáez et al, 2017). Transcriptome analysis of D. antarctica under abiotic stress demonstrated changes in the expression levels of stressresponsive genes (Lee et al, 2013a). The signaling pathways that mediate activation of the expression of the stressrelated genes responsible for the abiotic stress tolerance of this plant are unclear

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Discussion

Conclusion