In recent years, frequent occurrences of low temperature disasters due to global climate change have significantly impacted the normal growth of crops. Research has indicated that inorganic selenium (which is more toxic) can not only enhance the effects of low temperature stress but also increase selenium content on plants; however, there is a scarcity of studies investigating the impacts of organic selenium and nano-selenium on crops. In order to investigate whether organic selenium and nano-selenium can enhance low-temperature tolerance and increase selenium content in pak choi (Brassica chinensis var. pekinensis. cv. ‘Suzhouqing’), different concentrations (0, 5, 10, 20 mg L-1) of exogenous selenium were applied in this experiment to assess their effects on plant growth, nutritional quality and antioxidant properties. RNA-Seq technology was used to sequence the transcriptome of the leaves. Based on the transcriptome data, a Weighted Gene Co-expression Network Analysis (WGCNA) was employed to construct a network that associates with physiological traits related to stress resistance. Two highly correlated gene co-expression modules were identified, and within them, nine hub genes associated with endocytosis, antioxidant stress, absorption, transport, and metabolism of selenium were discovered. The results indicated that the beneficial effects on yield and total selenium content under low temperature were attributed to (1) protection of photosynthetic pigments for enhancing photosynthetic capacity by the up-regulation of LHca2, LHcb1, LHca1, LHcb4 in KEGG pathway: photosynthesis-antenna proteins; (2) activation of antioxidant system for efficient ROS homeostasis such as SOD, POD and CAT by the genes such as Superoxide dismutase, Monodehydroascorbate and (3) selenium absorption by endocytosis, seleninum transportation by ABC transporter gene family and selenium metabolism related genes such as Cysteine synthase, Glutaredoxin. These findings provide a foundation for further investigation into the molecular mechanisms underlying the effects of organic selenium and nano-selenium on cyanochloride production at low temperatures.

In order to investigate both the physiological and molecular mechanisms underlying the impacts of organic selenium and nano-selenium on drought stress of Pak Choi (Brassica chinensis var. pekinensis. cv. ‘Suzhouqing’), we measured photosynthetic pigment, antioxidant, nutritional quality, and performed transcriptome sequencing of leaves using RNA-seq technology. Under drought conditions, the beneficial effects of organic selenium and nano-selenium on weight and quality of ‘Suzhouqing’ were primarily manifested in the following aspects. Firstly, there was an enhancement in photosynthetic capacity through upregulation of light-trapping pigment proteins: Lhca1, Lhca2, Lhca3, Lhca4, Lhcb1, Lhcb2, Lhcb3, Lhcb4 and Lhcb5. Secondly, effective regulation of reactive oxygen species homeostasis was achieved by activating the antioxidant system via up-regulation of glutathione S-transferase. Thirdly, water homeostasis was maintained through glutathione oxidase activity. Lastly, increased expression levels of ABC transporter, adenylate kinase and cysteine desulphurase contributed to elevated total selenium content. In addition, we screened hub core genes related to the above key metabolic pathways through Weighted Gene Co-expression Network Analysis. Since the results were consistent with the up-regulated genes identified in the Kyoto Encyclopedia of Genes and Genomes pathway of differentially expressed genes by transcriptome sequencing analysis, this confirms the accuracy and reliability of the transcriptome sequencing data.