BackgroundMicroRNAs (miRNAs) play a vital role in growth, development, and stress response at the post-transcriptional level. Broccoli (Brassica oleracea L. var italic) is an important vegetable crop, and the yield and quality of broccoli are decreased by heat stress. The broccoli inbred lines that are capable of producing head at high temperature in summer are unique varieties in Taiwan. However, knowledge of miRNAomes during the broccoli head formation under heat stress is limited.MethodsIn this study, molecular characterization of two nearly isogenic lines with contrasting head-forming capacity was investigated. Head-forming capacity was better for heat-tolerant (HT) than heat-sensitive (HS) broccoli under heat stress.ResultsBy deep sequencing and computational analysis, 20 known miRNAs showed significant differential expression between HT and HS genotypes. According to the criteria for annotation of new miRNAs, 24 novel miRNA sequences with differential expression between the two genotypes were identified. To gain insight into functional significance, 213 unique potential targets of these 44 differentially expressed miRNAs were predicted. These targets were implicated in shoot apical development, phase change, response to temperature stimulus, hormone and energy metabolism. The head-forming capacity of the unique HT line was related to autonomous regulation of Bo-FT genes and less expression level of heat shock protein genes as compared to HS. For the genotypic comparison, a set of miRNAs and their targets had consistent expression patterns in various HT genotypes.ConclusionsThis large-scale characterization of broccoli miRNAs and their potential targets is to unravel the regulatory roles of miRNAs underlying heat-tolerant head-forming capacity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2201-1) contains supplementary material, which is available to authorized users.

BackgroundHead formation of broccoli (Brassica oleracea var. italica) is greatly reduced under high temperature (22 °C and 27 °C). Broccoli inbred lines that are capable of producing heads at high temperatures in summer are varieties that are unique to Taiwan. However, knowledge of the early-activated pathways of broccoli head formation under high temperature is limited.ResultsWe compared heat-tolerant (HT) and heat-sensitive (HS) transcriptome of broccoli under different temperatures. Weighted gene correlation network analysis (WGCNA) revealed that genes involved in calcium signaling pathways, mitogen-activated protein kinase (MAPK) cascades, leucine-rich repeat receptor-like kinases (LRR-RLKs), and genes coding for heat-shock proteins and reactive oxygen species homeostasis shared a similar expression pattern to BoFLC1, which was highly expressed at high temperature (27 °C). Of note, these genes were less expressed in HT than HS broccoli at 22 °C. Co-expression analysis identified a model for LRR-RLKs in survival-reproduction tradeoffs by modulating MAPK- versus phytohormones-signaling during head formation. The difference in head-forming ability in response to heat stress between HT and HS broccoli may result from their differential transcriptome profiles of LRR-RLK genes. High temperature induced JA- as well as suppressed auxin- and cytokinin-related pathways may facilitate a balancing act to ensure fitness at 27 °C. BoFLC1 was less expressed in HT than HS at 22 °C, whereas other FLC homologues were not. Promoter analysis of BoFLC1 showed fewer AT dinucleotide repeats in HT broccoli. These results provide insight into the early activation of stress- or development-related pathways during head formation in broccoli. The identification of the BoFLC1 DNA biomarker may facilitate breeding of HT broccoli.ConclusionsIn this study, HT and HS broccoli genotypes were used to determine the effect of temperature on head formation by transcriptome profiling. On the basis of the expression pattern of high temperature-associated signaling genes, the HS transcriptome may be involved in stress defense instead of transition to the reproductive phase in response to heat stress. Transcriptome profiling of HT and HS broccoli helps in understanding the molecular mechanisms underlying head-forming capacity and in promoting functional marker-assisted breeding.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1613-x) contains supplementary material, which is available to authorized users.

The higher anti-human immunodeficiency virus activity of a symmetrical 2,2 0disubstitued derivative of diphenyl disulfide (DPDS) has been explained by the lower energy of the lowest unoccupied molecular orbital (LUMO), resulted from a better hydrogen bond stabilization of the σ* SS bond orbital (BO). This conclusion entails the participation of σ* SS BO in constructing the LUMO. The higher content of σ* SS BO, compared to π* CC BOs of phenyl groups, in LUMO of DPDS has been found through analysis of the LUMO of DPDS expanded in the BO space. The high content of σ* SS BO (%σ* SS) in the LUMO of DPDS has laid the foundation for the formation of σ-type radical anion intermediate in the stepwise reductive cleavage of disulfide bond in the symmetrical 4,4 0-disubstitued DPDS derivatives. For the nine 4,4 0-disubstituted DPDS-derivatives under reductive cleavage studies, the increasing %σ* SS in the LUMOs is parallel to the increasing value of inner reorganization energy.