赤霉素对雌性大鼠早期生长发育及胰岛素样生长因子表达水平的影响

目的探讨植物生长调节剂赤霉素对雌性SD大鼠生长发育及胰岛素样生长因子(IGF-1)表达水平的影响。方法选择刚断乳雌性SD大鼠40只,随机分为4组,即对照组,低、中、高赤霉素剂量组,分别按照0、2、100和200mg/kg赤霉素剂量经口灌胃,连续15天,每天记录身长、体重、阴道开口情况。染毒结束,剖杀受试动物,获得肝脏、卵巢、子宫,计算脏器系数。提取肝组织RNA进行RT-PCR,检测肝内IGF-1、胰岛素样生长因子捆绑蛋白(IGFBP-1)基因的表达水平。结果各组间大鼠的身长、体重,阴道开口时间,子宫、卵巢的脏器系数差异无显著性(P>0.05),肝组织内IGF-1、IGFBP-1平均表达水平差异亦无显著性(P>0.05),但高剂量组部分样本出现IGF-1、IGFBP-1表达强度倒置的现象。高剂量组动物的肝脏系数小于对照组(P<0.05)。结论在0～200mg/kg剂量范围赤霉素接触对雌性SD大鼠生长发育、肝脏内IGF-1及其捆绑蛋白的表达影响不明显,但200mg/kg剂量的赤霉素摄入可能对其肝脏产生损伤。     

单性结实的分子研究进展

单性结实是人们获得无籽果实的有效途径之一,刺激性单性结实和单性结实品种的获得是目前行之有效的方法。基因单性结实植株具有可稳定遗传、结实率高、品质高、无畸形果、无籽果实等优势。针对单性结实的相关基因和蛋白进行综述,为转基因工程提供参考依据。     

不同处理方法对穿龙薯蓣种子萌发的影响

目的 研究低温砂层积处理后不同发芽温度(10、15、20、25、30℃)及不同质量浓度的赤霉素(GA3)和萘乙酸(NAA)对穿龙薯蓣种子萌发的影响.方法 采用培养皿培养法,对种子设置低温层积、不同质量浓度的GA3和NAA浸种处理,观察记录种子发芽率和发芽势并进行统计分析.结果 穿龙薯蓣种子经4℃低温砂层积后,在25℃条件下发芽率和发芽势最高,分别为80.00％和53.33％;而采用100 mg/L GA3直接浸泡未层积种子24 h,发芽率和发芽势可达66.65％和48.35％;1 mg/LNAA浸泡12h发芽率和发芽势为58.35％和43.35％;采用低温砂层积发芽进程最快,种子第6天开始发芽,第12天发芽完毕.结论 采用4℃低温砂层积60 d后在25℃下进行催芽或采用100 mg/L GA3进行催芽处理有利于穿龙薯蓣种子萌发.     

不同处理方法对穿龙薯蓣种子萌发的影响

目的 研究低温砂层积处理后不同发芽温度（10、15、20、25、30 ℃）及不同质量浓度的赤霉素（GA₃）和萘乙酸（NAA）对穿龙薯蓣种子萌发的影响。方法 采用培养皿培养法,对种子设置低温层积、不同质量浓度的GA₃和NAA浸种处理,观察记录种子发芽率和发芽势并进行统计分析。结果 穿龙薯蓣种子经4 ℃低温砂层积后,在25 ℃条件下发芽率和发芽势最高,分别为80.00%和53.33%;而采用100 mg/L GA₃直接浸泡未层积种子24 h,发芽率和发芽势可达66.65%和48.35%;1 mg/L NAA浸泡12 h发芽率和发芽势为58.35%和43.35%;采用低温砂层积发芽进程最快,种子第6天开始发芽,第12天发芽完毕。结论 采用4 ℃低温砂层积60 d后在25 ℃下进行催芽或采用100 mg/L GA₃进行催芽处理有利于穿龙薯蓣种子萌发。     

单叶蔓荆种子休眠特性研究

目的 研究单叶蔓荆种子休眠的原因及解除休眠的方法。方法 以单叶蔓荆的果实（蔓荆子）为材料,用石蜡切片法研究单叶蔓荆种子形态解剖学特点,通过种子吸胀和抑制物测试研究其休眠原因,采用浓硫酸和赤霉素（GA₃）处理打破种子休眠。结果 打破单叶蔓荆种子休眠的方法为GA₃处理,解除休眠的最佳方法为浓硫酸处理15 min,1.0 mg/mL GA₃浸种18 h,蛭石培养床30 ℃恒温培养能够达到发芽率78.7%。结论 蔓荆具有坚硬厚实的果皮,机械束缚是休眠的主要原因;果皮中含有萌发抑制物质,GA₃处理可有效解除单叶蔓荆种子的生理休眠。     

赤霉素对大鼠肝细胞线粒体呼吸功能的影响

目的探讨植物生长调节剂赤霉素对大鼠肝细胞线粒体呼吸功能的影响。方法 24只SD雄性大鼠随机分为4组,即对照组和3个赤霉素染毒组,各组动物分别用含0、40、160和640mg/kg赤霉素饲料喂养35天。染毒结束24h后处死动物,取大鼠肝,提取线粒体,分别用荧光分光光度法、紫外分光光度法、Clark氧电极测定线粒体膜电位变化、线粒体呼吸链复合体活性和线粒体呼吸功能的变化。结果高浓度赤霉素处理组大鼠肝细胞线粒体ComplexⅠ和ComplexⅢ活性以及中、高浓度赤霉素处理组肝细胞线粒体ComplexⅣ活性显著高于对照组(P<0.05)。高浓度赤霉素处理组大鼠肝细胞线粒体Ⅲ态耗氧量与对照组相比较差异有统计学意义(P<0.05)。结论动物摄入高浓度赤霉素饲料可使肝细胞线粒体呼吸功能增强。     

Gibberellins control fruit patterning in Arabidopsis thaliana

The Arabidopsis basic helix-loop-helix (bHLH) proteins INDEHISCENT (IND) and ALCATRAZ (ALC) specify tissues required for fruit opening that have major roles in seed dispersal and plant domestication. Here, we show that synthesis of the phytohormone gibberellin is a direct and necessary target of IND, and that ALC interacts directly with DELLA repressors, which antagonize ALC function but are destabilized by gibberellin. Thus, the gibberellin/DELLA pathway has a key role in patterning the Arabidopsis fruit, and the interaction between DELLA and bHLH proteins, previously shown to connect gibberellin and light responses, is a versatile regulatory module also used in tissue patterning.     

Arabidopsis semidwarfs evolved from independent mutations in GA20ox1, ortholog to green revolution dwarf alleles in rice and barley

Understanding the genetic bases of natural variation for developmental and stress-related traits is a major goal of current plant biology. Variation in plant hormone levels and signaling might underlie such phenotypic variation occurring even within the same species. Here we report the genetic and molecular basis of semidwarf individuals found in natural Arabidopsis thaliana populations. Allelism tests demonstrate that independent loss-of-function mutations at GA locus 5 (GA5), which encodes gibberellin 20-oxidase 1 (GA20ox1) involved in the last steps of gibberellin biosynthesis, are found in different populations from southern, western, and northern Europe; central Asia; and Japan. Sequencing of GA5 identified 21 different loss-of-function alleles causing semidwarfness without any obvious general tradeoff affecting plant performance traits. GA5 shows signatures of purifying selection, whereas GA5 loss-of-function alleles can also exhibit patterns of positive selection in specific populations as shown by Fay and Wu’s H statistics. These results suggest that antagonistic pleiotropy might underlie the occurrence of GA5 loss-of-function mutations in nature. Furthermore, because GA5 is the ortholog of rice SD1 and barley Sdw1/Denso green revolution genes, this study illustrates the occurrence of conserved adaptive evolution between wild A.thaliana and domesticated plants.Bioactive gibberellins (GAs) are plant growth regulators involved in important traits such as seed germination, flowering time, flower development, and elongation growth (1). GA biosynthesis and signaling pathways are well defined (1, 2) and have been targeted in crop breeding. Modification of GA pathways was crucial in the green revolution because it conferred semidwarfness, thus reducing lodging and increasing crop yields (3–6). Green revolution semidwarf varieties in wheat are due to mutations in DELLA genes, whereas many short straw rice varieties carry a mutation in the Semi-Dwarf-1 (SD1) locus. This locus codes for GA 20-oxidase-2, a GA biosynthesis gene that is also mutated in most modern barley varieties in which the gene was called Denso or Semi-dwarf 1 (Sdw1) (7).GA 20-oxidases are involved in the later steps of GA biosynthesis and belong to the group of 2-oxoglutarate–dependent dioxygenases that, together with GA 3-oxidases, form biologically active GA (8). Arabidopsis thaliana has five GA20ox paralogous genes. AtGA20ox-1, AtGA20ox-2, AtGA20ox-3, and AtGA20ox-4 can catalyze the in vitro conversion of GA₁₂ to GA₉. Therefore, GA20ox paralogs might have partial redundant functions (9). However, among paralog genes, only AtGA20ox-1 (GA5), which was cloned on the basis of the ga5 mutant (10), affected plant height (8).Natural variation for GA biosynthesis has been previously described in A. thaliana because the Bur-0 accession carries a loss-of-function allele at GA20ox4 (9), which does not result in a semidwarf phenotype. In addition, genetic variation in GA1 has been associated with variation in floral morphology (11). Furthermore, the semidwarf phenotype (here defined as a plant height shorter than half the size of genetically related individuals) observed in the Kas-2 accession is due to a recessive allele at the GA5 locus (12). The latter finding led to the questions of whether green revolution alleles, artificially selected in cereals, could also occur in natural populations of the wild species A. thaliana, and if so, how many different GA5 loss-of-function alleles exist, how they are distributed, and why they occur in some populations.