Dataset of protein changes induced by cold acclimation in red clover (Trifolium pratense L.) populations recurrently selected for improved freezing tolerance

Screening and isolation of cyclooxygenase-2 inhibitors from Trifolium pratense L. via ultrafiltration, enzyme-immobilized magnetic beads, semi-preparative high-performance liquid chromatography and high-speed counter-current chromatography

Nonsteroidal anti-inflammatory drugs reportedly reduce the risk of developing cancer. One mechanism by which they reduce carcinogenesis involves the inhibition of the activity of cyclooxygenase-2, an enzyme that is overexpressed in various cancer tissues. Its overexpression increases cell proliferation and inhibits apoptosis. However, selected cyclooxygenase-2 inhibitors can also act through cyclooxygenase-independent mechanisms. In this study, using ultrafiltration, enzyme-immobilized magnetic beads, high-performance liquid chromatography, and electrospray-ionization mass spectrometry, several isoflavonoids in Trifolium pratense L. extracts were screened and identified. Semi-preparative high-performance liquid chromatography and high-speed counter-current chromatography were then applied to separate the active constituents. Using these methods, seven major compounds were identified in Trifolium pratense L. As cyclooxygenase-2 inhibitors: rothindin, ononin, daidzein, trifoside, pseudobaptigenin, formononetin, and biochanin A, which were then isolated with >92% purity. This is the first report of the presence of potent cyclooxygenase-2 inhibitors in Trifolium pratense L. extracts. The results of this study demonstrate that the systematic isolation of bioactive components from Trifolium pratense L., by using ultrafiltration, enzyme-immobilized magnetic beads, semi-preparative high-performance liquid chromatography, and high-speed counter-current chromatography, represents a feasible and efficient technique that could be extended for the identification and isolation of other enzyme inhibitors.

Transcriptome analysis of leaf senescence in red clover (Trifolium pratense L.)

Red clover (Trifolium pratense L.) is an important cool-season legume plant, which is used as forage. Leaf senescence is a critical developmental process that negatively affects plant quality and yield. The regulatory mechanism of leaf senescence has been studied, and genes involved in leaf senescence have been cloned and characterized in many plants. However, those works mainly focused on model plants. Information about regulatory pathways and the genes involved in leaf senescence in red clover is very sparse. In this study, to better understand leaf senescence in red clover, transcriptome analysis of mature and senescent leaves was investigated using RNA-Seq. A total of about 35,067 genes were identified, and 481 genes were differentially expressed in mature and senescent leaves. Some identified differentially expressed genes showed similar expression patterns as those involved in leaf senescence in other species, such as Arabidopsis, Medicago truncatula and rice. Differentially expressed genes were confirmed by quantitative real-time PCR (qRT-PCR). Genes involved in signal transduction, transportation and metabolism of plant hormones, transcription factors and plant senescence were upregulated, while the downregulated genes were primarily involved in nutrient cycling, lipid/carbohydrate metabolism, hormone response and other processes. There were 64 differentially expressed transcription factor genes identified by RNA-Seq, including ERF, WRKY, bHLH, MYB and NAC. A total of 90 genes involved in biosynthesis, metabolism and transduction of plant hormones, including abscisic acid, jasmonic acid, cyokinin, brassinosteroid, salicylic acid and ethylene, were identified. Furthermore, 207 genes with direct roles in leaf senescence were demonstrated, such as senescence-associated genes. These genes were associated with senescence in other plants. Transcriptome analysis of mature and senescent leaves in red clover provides a large number of differentially expressed genes. Further analysis and identification of senescence-associated genes can provide new insight into the regulatory mechanisms of leaf development and senescence in legume plant and red clover.