人胎儿肝内甲胎蛋白的成份及其对T.B淋巴细胞发育的影响

本文用免疫组织化学方法,分别在冰冻和石蜡切片上,对24例不同胎龄的胎儿肝比较研究了肝内 AFP~+细胞数量及其与 T,B 淋巴细胞之间的关系。结果发现 AFP 仅分布于肝细胞内,其他细胞阴性。不同胎龄的肝脏,AFP 的染色强度和阳性率不同。17周前的胎肝,AFP~+细胞最多以后逐渐减少。出生前的肝脏内只有少数 AFP~+细胞。AFP~+细胞的多少与 B 细胞分化发育无多大关系,但与 T 细胞似乎关系密切,两者呈负相关,即 AFP~+细胞多时,T 细胞很少,AFP~+减少时,T 细胞增加,提示 AFP 对 T 细胞具有抑制作用。同时也证明 B 细胞在胎肝内受 T 细胞的影响不大,主要依赖于肝脏的微环境。另外对 AFP 的生物学意义也进行了讨论。     

Marker-assisted breeding of a photoperiod-sensitive male sterile <Emphasis Type="Italic">japonica</Emphasis> rice with high cross-compatibility with <Emphasis Type="Italic">indica</Emphasis> rice

The incomplete fertility of japonica × indica rice hybrids has inhibited breeders’ access to the substantial heterotic potential of these hybrids. As hybrid sterility is caused by an allelic interaction at a small number of loci, it is possible to overcome it by simple introgression at the major sterility loci. Here we report the use of marker-assisted backcrossing to transfer into the elite japonica cv. Zhendao88 a photoperiod-sensitive male sterility gene from cv. Lunhui422S (indica) and the yellow leaf gene from line Yellow249 (indica). The microsatellite markers RM276, RM455, RM141 and RM185 were used to tag the fertility genes S5, S8, S7 and S9, respectively. Line 509S is a true-breeding photoperiod-sensitive male sterile plant, which morphologically closely resembles the japonica type. Genotypic analysis showed that the genome of line 509S comprises about 92% japonica DNA. Nevertheless, hybrids between line 509S and japonica varieties suffer from a level of hybrid sterility, although the line is highly cross-compatible with indica types, with the resulting hybrids expressing a significant degree of heterosis. Together, these results suggest that segment substitution on fertility loci based on known information and marker-assisted selection are an effective approach for utilizing the heterosis of rice inter-subspecies.     

<Emphasis Type="Italic">FLOURY ENDOSPERM8</Emphasis>, encoding the UDP-glucose pyrophosphorylase 1, affects the synthesis and structure of starch in rice endosperm

Cereal opaque-kernel mutants are ideal genetic materials for studying the mechanism of starch biosynthesis and amyloplast development. Here we isolated and identified two allelic floury endosperm 8 (flo8) mutants of rice, named flo8-1 and flo8-2. In the flo8 mutant, the starch content was decreased and the normal physicochemical features of starch were altered. Map-based cloning and subsequent DNA sequencing analysis revealed a single nucleotide substitution and an 8-bp insertion occurred in UDP-glucose pyrophosphorylase 1 (Ugp1) gene in flo8-1 and flo8-2, respectively. Complementation of the flo8-1 mutant restored normal seed appearance by expressing full length coding sequence of Ugp1. RT-qPCR analysis revealed that Ugp1 was ubiquitously expressed. Mutation caused the decreased UGPase activity and affected the expression of most of genes associated with starch biosynthesis. Meanwhile, western blot and enzyme activity analyses showed the comparability of protein levels and enzyme activity of most tested starch biosynthesis related genes. Our results demonstrate that Ugp1 plays an important role for starch biosynthesis in rice endosperm.     

Albino midrib 1, encoding a putative potassium efflux antiporter,affects chloroplast development and drought tolerance in rice

Key message

Mutation of the AM1 gene causes an albino midrib phenotype and enhances tolerance to drought in rice

Abstract

K⁺ efflux antiporter (KEA) genes encode putative potassium efflux antiporters that are mainly located in plastid-containing organisms, ranging from lower green algae to higher flowering plants. However, little genetic evidence has been provided on the functions of KEA in chloroplast development. In this study, we isolated a rice mutant, albino midrib 1 (am1), with green- and white-variegation in the first few leaves, and albino midrib phenotype in older tissues. We found that AM1 encoded a putative KEA in chloroplast. AM1 was highly expressed in leaves, while lowly in roots. Chloroplast gene expression and proteins accumulation were affected during chlorophyll biosynthesis and photosynthesis in am1 mutants. Interestingly, AM1 was induced by salt and PEG, and am1 showed enhanced sensitivity to salinity in seed germination and increased tolerance to drought. Taken together, we concluded that KEAs were involved in chloroplast development and played important roles in drought tolerance.     

OsLOX2, a rice type I lipoxygenase,confers opposite effects on seed germination and longevity

Rice production and seed storage are confronted with grain deterioration and loss of seed viability. Some members of the lipoxygenase (LOX) family function in degradation of storage lipids during the seed germination, but little is known about their influence on seed longevity during storage. We characterized the role of rice OsLOX2 gene in seed germination and longevity via over-expression and knock-down approaches. Abundant expression of OsLOX2 was detected in panicles, roots, and stems, but not in leaves. Moreover, OsLOX2 was highly induced during germination. OsLOX2 protein, located in the cytoplasm, showed a wide range of temperature adaptation (20–50 °C) and a substrate preference to linoleic acid. Lines over-expressing OsLOX2 showed accelerated seed germination under normal condition and lower seed viability after accelerated aging. RNA interference (RNAi) of OsLOX2 caused delayed germination and enhanced seed longevity. RNAi lines with strongly repressed OsLOX2 activity completely lost the capability of germination after accelerated aging. More lipid hydroperoxide were found in OE15 than the control, but less in RNAi lines than in the WT Nipponbare. Therefore, OsLOX2 acts in opposite directions during seed germination and longevity during storage. Appropriate repression of the OsLOX2 gene may delay the aging process during the storage without compromising germination under normal conditions.     

Lowland Switchgrass Plants in Populations Set Completely Outcrossed Seeds Under Field Conditions as Assessed with SSR Markers

Switchgrass has long been characterized as an outcrossing species. However, mating behavior of plants in populations grown in the field allowing open pollination has not been documented. Accordingly, the objectives of this study were to determine the fertilization mode (i.e., selfing vs. outcrossing) of two self-compatible plants and to assess the mating behavior variability of lowland switchgrass genotypes in populations under field conditions. In Experiment I, two self-compatible genotypes ‘NL94 LYE 16?×?13’ and ‘SL93 7?×?15’ along with two populations were planted with two replications on the OSU Agronomy Research Farm, Stillwater, OK. Sixty-four progeny derived from half-sib seeds of each genotype per replication per year were genotyped with 4 to 20 simple sequence repeat (SSR) markers. In both 2010 and 2011, all progeny plants of the two parents were completely outcrossed exhibiting 100 % self-incompatibility. In Experiment II, two genetically narrow-based (NL94 C2-3 and SL93 C2-3), each having five parents, and two broad-based (NL94 C3 and SL93 C3), each comprising 26 parents, switchgrass populations with three replications were field established at the OSU Cimarron Valley Research Station, Perkins, OK. The DNA samples were isolated from 1700 open-pollinated progeny of 62 seed parents in 2010 and 773 progeny of 42 parents in 2011. Among all the progeny genotyped with eight to 16 SSR markers, only one was identified as a selfed progeny, indicating very little variability in outcrossing behavior under the field conditions. The identification of specific genotypes like NL94 LYE 16?×?13 and SL93 7?×?15 which are self-incompatible in the open field but self-compatible under the controlled conditions potentially enables efficient production of F1 hybrid seed in switchgrass.     

Pyrophosphate: fructose-6-phosphate 1-phosphotransferase (PFP) regulates carbon metabolism during grain filling in rice

Key message

Decreased PFPase activity in rice perturbs the equilibration of carbon metabolism during grain filling but has no visible phenotypic effects during the vegetative and reproductive growth stages.

Abstract

Starch is a primary energy reserve for various metabolic processes in plant. Despite much advance has been achieved in pathways involved in starch biosynthesis, information was still lacked for precise regulation related to carbon metabolism during seed filling in rice (Oryza sativa). The objective of this study was to identify and characterize new gene associated with carbon metabolism during grain filling. By screening our chemical mutant pool, two allelic mutants exhibiting floury endosperm were isolated. No visible phenotypic defects were observed during both the vegetative and reproductive growth stages, except for the floury-like endosperm of grains with significantly reduced kernel thickness, 1000-grain weight and total starch content. Map-based cloning revealed that the mutant phenotypes were controlled by a gene encoding pyrophosphate: fructose-6-phosphate 1-phosphotransferase (PFP, EC 2.7.1.90) β subunit (PFP_β), which catalyzes reversible interconversion between fructose-6-phosphate and fructose-1, 6-bisphosphate. The identity of PFP _β was further confirmed by a genetic complementation test. Subcellular analysis demonstrated that PFPβ was localized in cytoplasm. Quantitative PCR and histochemical staining indicated PFP _β was ubiquitously expressed in various tissues. Furthermore, we found PFP _β could express in both the early and late phases of starch accumulation during grain filling and decreased activity of PFP _β in pfp mutants resulted in compromised carbon metabolism with increased soluble sugar contents and unfavorable starch biosynthesis. Our results highlight PFP_β functions in modulating carbon metabolism during grain filling stage.

     

优化的复合自动诱导培养基（CAI-4）对外源蛋白在大肠杆菌中 表达的影响

[目的]原核表达系统是目前最为广泛使用的一种外源蛋白表达系统。在利用原核表达系统表达目的蛋白的过程中,可溶性外源蛋白的产量是决定成本和效率的决定性因素。[方法]本项研究中利用本实验室构建的7种不同的重组质粒(-1、p-2、p-3、p-4、p-5、p-6、p-7),检测其在复合自动诱导培养基中的表达情况,评价哪一种培养基更适合于外源蛋白的表达,提高目的蛋白的产量。[结果]结果显示,这7种重组蛋白在复合自动诱导培养基的表达量是普通LB培养基的4~8倍;并在此基础上,对复合培养基的成份进行进一步优化,形成了一种优化培养基(改良培养基-4),P-1、P-2、P-3这3种融合蛋白在这种改良培养基中的表达量比优化前提高了至少2倍。     

Identification of Indica rice chromosome segments for the improvement of Japonica inbreds and hybrids

Exploitation of heterosis has brought significant advance in plant breeding and agricultural production, although its genetic basis is still poorly understood. In this study, a total of 66 chromosome segment substitution (CSS) lines, derived from a cross between japonica rice inbred line Asominori (as the recurrent parent) and indica rice inbred line IR24 (as the donor parent), were used to investigate the genetic basis of heterosis in indica × japonica inter-subspecific rice hybrids. Each CSS line was crossed with the background parent Asominori, and the heterosis of F(1) hybrids was estimated by comparing the F(1) performance with its two parental lines. Field experiments were carried out across six different environments to evaluate yield and yield-related traits in the 66 CSS lines and their 66 corresponding F(1) hybrids. Quantitative trait loci (QTL) analyses were conducted using a likelihood ratio test based on the stepwise regression. Thirty-six QTL were identified with significant effects in CSSL, 21 with significant effects in hybrids and 13 with significant effects in both. On the basis of average dominance degree, of all the 70 QTL affecting yield-related agronomic traits, 28.6% (20) showed an overdominance, 35.7% (25) a partial dominance and 30% (21) an additive effect, indicating that all effects contribute to trait variation in japonica-indica rice hybrids. Effects of these QTL were examined to identify Indica rice chromosome segments of interest for the improvement of japonica inbred lines and hybrids.