Direct Construction of C-Alkyl Glycosides from Non-Activated Olefins via Nickel-Catalyzed C(sp3)─C(sp3) Coupling Reaction.

Among C-glycosides, C-alkyl glycosides are significant building blocks for natural products and glycopeptides. However, research on efficient construction methods for C-alkyl glycosides remains relatively limited. Compared with Michael acceptors, non-activated olefins are more challenging substrates and have rarely been employed in the construction of C-glycosides. Here, a highly efficient and convenient approach for the synthesis of C-alkyl glycosides through a nickel-catalyzed C(sp3)-C(sp3) coupling reaction is presented. A distinctive feature of this method is its utilization of non-activated olefins as the anomeric radical acceptors for hydroalkylation, allowing for the direct formation of C-glycoside bonds in a single step. Furthermore, this method demonstrates excellent compatibility with a broad scope of highly reactive functional groups. Mechanistic investigations suggest that the reaction proceeds via a free radical pathway, leading predominantly to the formation of products with α-configuration. Overall, this innovative methodology offers a versatile and practical approach for the synthesis of C-alkyl glycosides, offering new avenues for the production of intricate glycosides with potential applications in drug discovery and chemical biology.

Zearalenone Induces Blood-Testis Barrier Damage through Endoplasmic Reticulum Stress-Mediated Paraptosis of Sertoli Cells in Goats.

Zearalenone (ZEA) is present worldwide as a serious contaminant of food and feed and causes male reproductive toxicity. The implication of paraptosis, which is a nonclassical paradigm of cell death, is unclear in ZEA-induced male reproductive disorders. In this study, the toxic effects of ZEA on the blood-testis barrier (BTB) and the related mechanisms of paraptosis were detected in goats. ZEA exposure, in vivo, caused a significant decrease in spermatozoon quality, the destruction of seminiferous tubules, and damage to the BTB integrity. Furthermore, ZEA exposure to Sertoli cells (SCs) in vitro showed similar dysfunction in structure and barrier function. Importantly, the formation of massive cytoplasmic vacuoles in ZEA-treated SCs corresponded to the highly swollen and dilative endoplasmic reticulum (ER), and paraptosis inhibition significantly alleviated ZEA-induced SC death and vacuolization, which indicated the important contribution of paraptosis in ZEA-induced BTB damage. Meanwhile, the expression of ER stress marker proteins was increased after ZEA treatment but decreased under the inhibition of paraptosis. The vacuole formation and SC death, induced by ZEA, were remarkably blocked by ER stress inhibition. In conclusion, these results facilitate the exploration of the mechanisms of the SC paraptosis involved in ZEA-induced BTB damage in goats.

Effects of exogenous methyl jasmonate on the synthesis of endogenous jasmonates and the regulation of photosynthesis in citrus.

Methyl jasmonate (MeJA) is an airborne signaling phytohormone that can induce changes in endogenous jasmonates (JAs) and cause photosynthetic responses. However, the response of these two aspects of citrus plants at different MeJA concentrations is still unclear. Four MeJA concentrations were used in two citrus varieties, Huangguogan (C. reticulata × C. sinensis) and Shiranuhi [C. reticulata × (C. reticulata × C. sinensis)], to investigate the effects of MeJA dose on the endogenous JAs pathway and photosynthetic capacity. We observed that MeJA acted in a dose-dependent manner, and its stimulation in citrus leaves showed a bidirectional character at different concentrations. This work demonstrates that MeJA at only a concentration of 2.2 mM or less contributed to the activation of magnesium protoporphyrin IX methyltransferase (ChlM, EC 2.1.1.11) and protochlorophyllide oxidoreductase (POR, EC 1.3.1.11) and the simultaneous accumulation of Chl a and Chl b, which in turn contributed to an improved photosynthetic capacity and PSII photochemistry efficiency of citrus. Meanwhile, the inhibition of endogenous JAs synthesis by exogenous MeJA was observed. This was achieved by reducing the ratio of monogalactosyl diacylglycerol (MGDG) to diagalactosyl diacylglycerol (DGDG) and inhibiting the activities of key enzymes in JAs synthesis, especially 12-oxo-phytodienoic acid reductase (OPR, EC 1.3.1.42). Another noteworthy finding is that there may exist a JA-independent pathway that could regulate 12-oxo-phytodienoic acid (OPDA) synthesis. This study jointly analyzed the internal hormone regulation mechanism and the external physiological response, as well as revealed the effects of exogenous MeJA on promoting the photosynthesis and inhibiting the endogenous JAs synthesis.

Effects of interstocks on growth and photosynthetic characteristics in 'Yuanxiaochun' Citrus seedlings.

To obtain the compatibility of interstocks crossing with 'Yuanxiaochun', we performed a comparative analysis with five interstocks. From the 60th to 240th day after grafting, there was a significant difference between different treatments. All the new shoot/interstock diameter ratios were <1, indicating that there was no obvious phenomenon of small feet in 'Yuanxiaochun' seedlings of five kinds of interstocks. The density of 'Yuanxiaochun' was significantly different. Chl a, Chl b, T-Chl content of 'Shiranuhi', 'Harumi', 'Tarocco' changed greatly from the 90th to 120th day after grafting. The intercellular CO2 concentration (Ci) of 'Shiranuhi' was significantly higher than the other interstocks. In addition, when 'Yuanxiaochun' was grafted onto 'Shiranuhi', net photosynthetic rate (Pn), stomatal conductance (gs) and tanspiration rate (Tr) were higher. When 'Harumi' were used as the interstocks of 'Yuanxiaochun', the light saturation point (LSP) value was larger, which was conducive to the utilisation of strong light. Moreover, the value of LSP-LCP (LCP, light compensation point) of 'Harumi' and 'Tarocco' were significantly higher than the other three interstocks. The apparent quantum efficiency (AQE), RuBP maximum regeneration rate (Jmax) and maximum carboxylation efficiency of Rubisco (Vcmax) value of 'Shiranuhi' was significantly lower than that of 'Ponkan'. The CO2 compensation point (CCP) of 'Harumi' interstock was lower, but the CO2 saturation point (CSP) of 'Tarocco' interstock was higher than those of other interstocks respectively. There was a small difference in initial fluorescence (F0) of different interstocks. The maximal photochemical efficiency of PSII in the dark (Fv/Fm) of 'Kumquat' was the lowest. In addition, Both Y(II) and ETR values of the 'Yuanxiaochun' leaves of 'Ponkan' interstock was the largest one. However, the non-photochemical quenching (qN) of 'Ponkan' was significantly lower, and that of 'Tarocco' interstock was the highest one. Interstocks have different effect on the growth and development, photosynthetic characteristics related to physiological characteristics of 'Yuanxiaochun' trees. 'Ponkan' and 'Kumquat' as the interstock of 'Yuanxiaochun' was more conducive to the rapid accumulation of photosynthetic products for normal vegetative and reproductive growth of plants.