A key issue to be addressed in stem cell biology is the molecular signaling mechanism controlling embryonic stem （ES） cell pluripotency. Stem cell properties are dictated by specific transcription factors and epigen...A key issue to be addressed in stem cell biology is the molecular signaling mechanism controlling embryonic stem （ES） cell pluripotency. Stem cell properties are dictated by specific transcription factors and epigenetic processes such as DNA methylation and chromatin remodeling. Several cytokines/growth factors have been identified as critical ES cell regulators. However, there is a gap in our knowledge of the intracellular signaling pathways linking extracellular signals to transcriptional regulation in ES cells. This short review discusses the physiological role of Shp2, a cytoplasmic tyro- sine phosphatase, in the molecular switch governing ES cell self-renewal versus differentiation. Shp2 promotes ES cell differentiation, mainly through bi-directional modulation of Erk and Stat3 pathways. Deletion of Shp2 in mouse ES cells results in more efficient self-renewal. This observation provides the impetus to develop Shp2 inhibitors for maintenance and amplification of ES cells in culture.展开更多
Seeds from Tabebuia roseo-alba lose viability very fast. Moreover, the seed germination rate is very low, reaching approximately 40%. This study aimed at the in vitro induction of embryogenic callus. This technology a...Seeds from Tabebuia roseo-alba lose viability very fast. Moreover, the seed germination rate is very low, reaching approximately 40%. This study aimed at the in vitro induction of embryogenic callus. This technology allows subsequent plant regeneration as an alternative for the production of T. roseo-alba seedlings. Seeds were germinated in vitro and after 20 days, cotyledonary leaves, hypocotyls and root segments excised from these seedlings were used as explants. They were inoculated on MS medium supplemented with sucrose （30 g/L）, agar （5.0 g/L） and different auxins. The effect of 2,4-D, picloram and NAA at concentrations 0.0, 0.5, 1.0, 2.0 and 4.0 mg/L was evaluated. For the analysis of callus with embryogenic characteristics, ultra-structural study by scanning electron microscopy and cytochemical test with carmine were performed. The results showed that the culture medium supplemented with 4 mg/L NAA presented induction of callus with embryogenic characteristics in all explants used, with cotyledonary leaves showing the highest percentage （70% of explants with embryogenic characteristics）. The use of 2, 4-D and picloram was efficient for callus formation in different explants, but no embryogenic characteristics were observed. From the ultra-structural analysis of callus with embryogenic characteristics, it was found that cells from different explant sources had isodiametric format. This format is similar to somatic embryos in globular stage. The cytochemical analysis confirmed the presence of pro-embryogenic cells in callus mass. Callus induced from cotyledonary leaves presented 46% positive reaction to carmine acetic.展开更多
[Objective]As a mosquito-repelling ornamental plant,Pelargonium×Citrosum Vanleenii(P.× Citrosum Vanleenii)is hard to be acquired because of its hybrid background,the paper was to a new regeneration system of...[Objective]As a mosquito-repelling ornamental plant,Pelargonium×Citrosum Vanleenii(P.× Citrosum Vanleenii)is hard to be acquired because of its hybrid background,the paper was to a new regeneration system of(P.× Citrosum Vanleenii).[Method] By studying the influence of plant growth regulators(PGRs)on explant type(leaves and petioles),the optimal combinations of PGRs to maximize SELSs(somatic embryo-like structure)and buds were established.[Result]0.2 mg/L NAA+1.0 mg/L BA was best for LS(leaves segments)and 0.2 mg/L NAA + 1.5 mg/L BAs was best for PS(petioles segments).Cultured plantlets were successfully acclimatized in soil where they grew normally without any morphological variation.Although both LS and PS were usable,the leaf was a better explant for induction of embryogenic calli,somatic embryo-like structures and buds.[Conclusion]This work offered a rapid and efficient system for plant regeneration of P.×Citrosum Vanleenii.展开更多
Long juvenile phase and lack of effective protocols for large scale vegetative propagation are limitations to domestication and improvement of the shea tree. The present study seeks to develop a protocol for plant reg...Long juvenile phase and lack of effective protocols for large scale vegetative propagation are limitations to domestication and improvement of the shea tree. The present study seeks to develop a protocol for plant regeneration of shea （Vitellaria paradoxa） from immature cotyledon explants. Embryogenic callus cultures were induced on Murashige and Skoog medium （MS） containing 3% sucrose, 0.24% Phytagel, and various concentrations of 2,4-Dichlorophenoxyacetic acid （2,4-D） after four weeks of culture in darkness. Rates of embryogenic callus induction were significantly affected by the addition of 2, 4-D to the medium. Within 28 days of culture, the highest percentage of embyogenic calli （77.61%） occurred on MS media containing 0.45 ~tM of 2,4-D in the dark. Somatic embryos were obtained by culturing embryogenic callus （in the dark） on MS medium fortified with 3% sucrose, 0.24% phytagel and devoid of growth regulators. Culturing at 16 h photoperiod restricted both the induction of embryogenic calli cultures and somatic embryos. Somatic embryos germinated, developed shoots and rooted vigorously on MS medium devoid of growth regulators. Germinated plantlets were acclimatized, successfully.展开更多
文摘A key issue to be addressed in stem cell biology is the molecular signaling mechanism controlling embryonic stem （ES） cell pluripotency. Stem cell properties are dictated by specific transcription factors and epigenetic processes such as DNA methylation and chromatin remodeling. Several cytokines/growth factors have been identified as critical ES cell regulators. However, there is a gap in our knowledge of the intracellular signaling pathways linking extracellular signals to transcriptional regulation in ES cells. This short review discusses the physiological role of Shp2, a cytoplasmic tyro- sine phosphatase, in the molecular switch governing ES cell self-renewal versus differentiation. Shp2 promotes ES cell differentiation, mainly through bi-directional modulation of Erk and Stat3 pathways. Deletion of Shp2 in mouse ES cells results in more efficient self-renewal. This observation provides the impetus to develop Shp2 inhibitors for maintenance and amplification of ES cells in culture.
文摘Seeds from Tabebuia roseo-alba lose viability very fast. Moreover, the seed germination rate is very low, reaching approximately 40%. This study aimed at the in vitro induction of embryogenic callus. This technology allows subsequent plant regeneration as an alternative for the production of T. roseo-alba seedlings. Seeds were germinated in vitro and after 20 days, cotyledonary leaves, hypocotyls and root segments excised from these seedlings were used as explants. They were inoculated on MS medium supplemented with sucrose （30 g/L）, agar （5.0 g/L） and different auxins. The effect of 2,4-D, picloram and NAA at concentrations 0.0, 0.5, 1.0, 2.0 and 4.0 mg/L was evaluated. For the analysis of callus with embryogenic characteristics, ultra-structural study by scanning electron microscopy and cytochemical test with carmine were performed. The results showed that the culture medium supplemented with 4 mg/L NAA presented induction of callus with embryogenic characteristics in all explants used, with cotyledonary leaves showing the highest percentage （70% of explants with embryogenic characteristics）. The use of 2, 4-D and picloram was efficient for callus formation in different explants, but no embryogenic characteristics were observed. From the ultra-structural analysis of callus with embryogenic characteristics, it was found that cells from different explant sources had isodiametric format. This format is similar to somatic embryos in globular stage. The cytochemical analysis confirmed the presence of pro-embryogenic cells in callus mass. Callus induced from cotyledonary leaves presented 46% positive reaction to carmine acetic.
基金Supported by Fund of Jinhua Science Technology Foundation of China(2009-2-02)
文摘[Objective]As a mosquito-repelling ornamental plant,Pelargonium×Citrosum Vanleenii(P.× Citrosum Vanleenii)is hard to be acquired because of its hybrid background,the paper was to a new regeneration system of(P.× Citrosum Vanleenii).[Method] By studying the influence of plant growth regulators(PGRs)on explant type(leaves and petioles),the optimal combinations of PGRs to maximize SELSs(somatic embryo-like structure)and buds were established.[Result]0.2 mg/L NAA+1.0 mg/L BA was best for LS(leaves segments)and 0.2 mg/L NAA + 1.5 mg/L BAs was best for PS(petioles segments).Cultured plantlets were successfully acclimatized in soil where they grew normally without any morphological variation.Although both LS and PS were usable,the leaf was a better explant for induction of embryogenic calli,somatic embryo-like structures and buds.[Conclusion]This work offered a rapid and efficient system for plant regeneration of P.×Citrosum Vanleenii.
文摘Long juvenile phase and lack of effective protocols for large scale vegetative propagation are limitations to domestication and improvement of the shea tree. The present study seeks to develop a protocol for plant regeneration of shea （Vitellaria paradoxa） from immature cotyledon explants. Embryogenic callus cultures were induced on Murashige and Skoog medium （MS） containing 3% sucrose, 0.24% Phytagel, and various concentrations of 2,4-Dichlorophenoxyacetic acid （2,4-D） after four weeks of culture in darkness. Rates of embryogenic callus induction were significantly affected by the addition of 2, 4-D to the medium. Within 28 days of culture, the highest percentage of embyogenic calli （77.61%） occurred on MS media containing 0.45 ~tM of 2,4-D in the dark. Somatic embryos were obtained by culturing embryogenic callus （in the dark） on MS medium fortified with 3% sucrose, 0.24% phytagel and devoid of growth regulators. Culturing at 16 h photoperiod restricted both the induction of embryogenic calli cultures and somatic embryos. Somatic embryos germinated, developed shoots and rooted vigorously on MS medium devoid of growth regulators. Germinated plantlets were acclimatized, successfully.
