Abstract
BackgroundLow temperature is a major factor influencing the growth and development of Chinese jujube (Ziziphus jujuba Mill.) in cold winter and spring. Little is known about the molecular mechanisms enabling jujube to cope with different freezing stress conditions. To elucidate the freezing-related molecular mechanism, we conducted comparative transcriptome analysis between ‘Dongzao’ (low freezing tolerance cultivar) and ‘Jinsixiaozao’ (high freezing tolerance cultivar) using RNA-Seq.ResultsMore than 20,000 genes were detected at chilling (4 °C) and freezing (− 10 °C, − 20 °C, − 30 °C and − 40 °C) stress between the two cultivars. The numbers of differentially expressed genes (DEGs) between the two cultivars were 1831, 2030, 1993, 1845 and 2137 under the five treatments. Functional enrichment analysis suggested that the metabolic pathway, response to stimulus and catalytic activity were significantly enriched under stronger freezing stress. Among the DEGs, nine participated in the Ca2+ signal pathway, thirty-two were identified to participate in sucrose metabolism, and others were identified to participate in the regulation of ROS, plant hormones and antifreeze proteins. In addition, important transcription factors (WRKY, AP2/ERF, NAC and bZIP) participating in freezing stress were activated under different degrees of freezing stress.ConclusionsOur research first provides a more comprehensive understanding of DEGs involved in freezing stress at the transcriptome level in two Z. jujuba cultivars with different freezing tolerances. These results may help to elucidate the molecular mechanism of freezing tolerance in jujube and also provides new insights and candidate genes for genetically enhancing freezing stress tolerance.
Highlights
Low temperature is a major factor influencing the growth and development of Chinese jujube (Ziziphus jujuba Mill.) in cold winter and spring
Quality analysis and sequence assembly of RNA sequencing (RNA-seq) data Total RNA extracted from the xylem of jujube branches was employed to build expression libraries for sequencing by using the Illumina High-Seq sequencing system
Regarding transcription factors, through the analysis of differentially expressed genes (DEGs), we found that the genes belonging to the NAC, WRKY, MYB, AP2/ERF and bHLH families all showed a significant up- or downregulation
Summary
Low temperature is a major factor influencing the growth and development of Chinese jujube (Ziziphus jujuba Mill.) in cold winter and spring. Hydrogen peroxide (H2O2), superoxide anion (O2−), and hydroxyl radical (HO·) [25,26,27,28,29,30] as ROS signals can activate redox-responsive proteins, such as protein kinases and transcription factors, such as MAPK cascade [10], and activate of ZAT12 [31]. He et al [32] found that PeSTZ1 could enhance freezing tolerance through modulation of ROS scavenging by directly regulating PeAPX2 in Populus euphratica
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