Inter-Alu-like species-specific sequences in the Saccharum complex

Alu sequences constitute the most abundant family of short interspersed nuclear elements, SINEs, in the primate genome. The Alu-PCR method, which consists of amplification between Alu sequences, is usually applied in human genetics to provide polymorphic markers. Here we report the presence of Alu-like sequences in sugarcane and related species by applying the Alu-PCR-like method. Amplifications using a PCR primer defined in conserved regions of Alu human sequences lead to specific complex multiband profiles in all the Saccharum and related genera clones surveyed. The isolation and characterisation of the amplified genus-specific inter-Alu-like fragments allowed us to isolate repeated sequences that are specific for different genera of the Saccharum complex: MsCIR2 from Miscanthus, EaCIR6 and EaCIR7 from Erianthus, and SrCIR2 from Saccharum. Two PCR diagnostic tests were developed from the inter-Alu-like sequences MsCIR2 and EaCIR6, and proved efficient in identifying intergeneric hybrids Saccharum×Miscanthus or Saccharum×Erianthus, respectively. The present study illustrates how the Alu-PCR-like method could help investigating the origin of amphiploid species and monitoring introgression in plants. Received: 7 March 1999 / Accepted: 25 March 1999     

Characteristics of ATPase from sugarcane protoplast and vacuole membranes

Characteristics of membrane-associated ATPase from commercial Hawaiian varieties of sugarcane ( Saccharum spp. hybrids) were investigated in preparations from sugarcane cell suspension culture and from stalk tissues of the intact plant. In order to examine comparable preparations, protoplasts and vacuoles, in turn, were obtained from both sources. ATPase from preparations of crude protoplast membranes and tonoplast had a pH optimum of 6 to 6.5. The relative effectiveness of divalent cations in stimulating ATPase was Mg²⁺ > Mn²⁺≥ Co²⁺ > Ca²⁺≥ Zn²⁺. Enzyme activity was not stimulated by K⁺, nor by other monovalent cations. Protoplasts and vacuoles from both sources showed significant acid phosphatase activity. Acid phosphatase activity was inhibited by molybdate, but ATPase activity was unaffected. Membrane preparations from protoplasts contained inorganic pyrophosphatase, but enzyme activity was low or not present in tonoplast preparations. Cell suspension and stalk tissue preparations hydrolyzed a large number of nucleoside di- and triphosphates. The hydrolysis is most likely due to a series of enzymes rather than a single enzyme. ATPase from protoplast and tonoplast preparations was inhibited 30–50% by diethylstilbestrol and sodium ortho-vanadate and was unaffected by ionophores. This study illustrates the complexity of phosphohydrolase activities in membrane preparations from sugarcane. The study, however, also illustrates substantial similarity in the behavior of these enzymes, whether they are derived from the plant itself or from cell cultures originating from comparable tissues of the plant.     

Stomatal response to blue light: water use efficiency in sugarcane and soybean*

Abstract. The significance of blue light-stimulated stomatal conductance for carbon assimilation (A), stomatal conductance (g), intercellular CO₂ (C_i), stomatal limitation of A (L), transpiration (E) and water use efficiency (W = A/E), was determined in a C₄ and a C₃ species. W and L were evaluated for steady-state gas exchange with constant, saturating red light (A_s, g_s, E_s), and for the integrated gas exchange above the steady state baseline induced by a single, brief pulse of blue light (A_p, g_p, E_p). Sugarcane (Saccharum spp. hybrid), a C₄ grass, and soybean (Glycine max) a C₃ dicot, were compared. Sugarcane exhibited typical C₄ behaviour, with A saturing at C_i of ca. 200 μmol mol^?1, compared to >500 μmol mol^?1 in soybean. Steady-state W was also considerably higher in sugarcane. The extent of stomatal opening in response to a blue light pulse, from baseline (g_s) to the maximum value of conductance during the opening response (g_m), was similar in the two species. More rapid opening and closing of stomata in sugarcane resulted in a smaller integrated magnitude of the conductance response (g_p) than in soybean. At the peak of the blue light response, both species exhibited similar levels of L. During the response to the pulse of blue light, A and C_i increased and L decreased to a greater extent in sugarcane than in soybean. As a result, the gas exchange attributed to the stomatal response to blue light exhibited a higher ratio of A_p to E_p (W_p) in sugarcane than in soybean. This W_p was lower in both species than was the W_s associated with the steady state gas exchange. The two species did not differ in the rate of induction of photosynthetic utilization of elevated C_i. The greater stimulation of A in sugarcane was attributed to its C₄ attributes of greater carboxylation efficiency (slope of the A versus C_i relationship), lower g_s and prevailing C_i,s, and greater L_s under steady-state red illumination. Despite saturation of A at low levels of C_i in C₄ species, the gas exchange attributed to the stomatal response to blue light decreased L and contributed considerably to carbon acquisition, while maintaining the high level of W associated with C₄ metabolism.     

云南割手密血缘F1代创新种质的因子和聚类分析

本试验对70份云南割手密血缘F1代创新种质材料8个工农艺性状进行了因子和聚类分析。因子分析中8个公因子保留前3个公因子,其累计贡献率达79.35%。第1公因子中载荷值较大的是单产、含糖量、公顷有效茎数、出苗率和分蘖率等性状;第2公因子中起主导作用的性状是茎径和株高两个产量因子;第3公因子只有11月理论蔗糖分起主导作用。以70份创新材料3个公因子的因子得分为指标,采用系统聚类中的最长距离法进行系统聚类分析。在遗传距离2.4处,参试材料被聚为十类,其中占参试材料总数的38.6%的第Ⅰ、Ⅳ、Ⅶ、Ⅷ、Ⅹ五类材料,表现高产;占参试材料82.8%的第Ⅰ、Ⅱ、Ⅳ、Ⅴ、Ⅵ、Ⅶ、Ⅸ七类材料,表现高糖,特别是其中占参试材料52.8%的Ⅰ、Ⅳ、Ⅴ、Ⅵ四类材料,11月理论蔗糖分均高于12%;占参试材料总数30%的第I、Ⅳ、Ⅶ三类材料,表现高产、高糖。这个分类结果为有针对性的利用这些创新种质材料培育高产、高糖创新亲本提供了科学依据。     

连续两年UV-B辐射增强对割手密叶绿素含量的影响

研究了大田栽培和自然光条件下,连续两年模拟紫外辐射(UV-B,280~315 nm)增加对92-11和93-25两个割手密无性系叶绿素含量的影响。结果表明,割手密92-11在UV-B辐射的影响下,叶绿素含量降低,而割手密93-25抗性很强,在增加了5 kJ/m2UV-B辐射下,其叶绿素含量增加。割手密叶绿素含量对UV-B辐射的响应具有种内差异。割手密92-11对紫外辐射的抗性在2004年比2003年强,而割手密93-25则相反。生育期中开花期受UV-B辐射影响最大,然后是分蘖期,伸长期抗性较强。     

甘蔗杂交后代蔗汁品质性状的遗传分析

以4×3不完全双列杂交(NCⅡ)选配的12个杂交组合后代为材料,对蔗汁锤度、旋光读数、转光度、蔗汁蔗糖分、视纯度和重力纯度等6个品质性状进行配合力和遗传力分析。结果表明,品质性状的遗传主要由基因加性效应引起,其中蔗汁锤度、旋光读数、转光度、蔗汁蔗糖分主要由父本基因加性效应引起。CP72-330、HoCP93-750、桂糖91-116和粤糖92-1287等4个亲本的品质性状一般配合力(gca)为正值且较大,是配合力较好的高糖亲本。CP72-330×桂糖91-116及HoCP93-750×粤糖92-1287的品质性状特殊配合力(sca)相对效应值均为正值且较大,杂交后代品质性状平均值也较高,为较好的高糖杂交组合。品质性状父本gca方差大于母本gca方差,亲本gca方差为组合sca方差的7-28倍,广义遗传力(hB2)为58%-68%,狭义遗传力(hN2)为56%-60%,属于遗传能力较强的品质性状。     

Towards a dynamic photosynthesis model to guide yield improvement in C4 crops

The most productive C4 food and biofuel crops, such as Saccharum officinarum (sugarcane), Sorghum bicolor (sorghum) and Zea mays (maize), all use NADP-ME-type C4 photosynthesis. Despite high productivities, these crops fall well short of the theoretical maximum solar conversion efficiency of 6%. Understanding the basis of these inefficiencies is key for bioengineering and breeding strategies to increase the sustainable productivity of these major C4 crops. Photosynthesis is studied predominantly at steady state in saturating light. In field stands of these crops light is continually changing, and often with rapid fluctuations. Although light may change in a second, the adjustment of photosynthesis may take many minutes, leading to inefficiencies. We measured the rates of CO₂ uptake and stomatal conductance of maize, sorghum and sugarcane under fluctuating light regimes. The gas exchange results were combined with a new dynamic photosynthesis model to infer the limiting factors under non-steady-state conditions. The dynamic photosynthesis model was developed from an existing C4 metabolic model for maize and extended to include: (i) post-translational regulation of key photosynthetic enzymes and their temperature responses; (ii) dynamic stomatal conductance; and (iii) leaf energy balance. Testing the model outputs against measured rates of leaf CO₂ uptake and stomatal conductance in the three C4 crops indicated that Rubisco activase, the pyruvate phosphate dikinase regulatory protein and stomatal conductance are the major limitations to the efficiency of NADP-ME-type C4 photosynthesis during dark-to-high light transitions. We propose that the level of influence of these limiting factors make them targets for bioengineering the improved photosynthetic efficiency of these key crops.     

Strong correlation of wild barley (Hordeum spontaneum) population structure with temperature and precipitation variation

In this study, we present the genetic analysis of a new collection of wild barley ( Hordeum spontaneum ) using 42 simple sequence repeat (SSR) markers that represent the seven chromosomes. The Barley1K (B1K) infrastructure consists of 1020 accessions collected in a hierarchical sampling mode (HSM) from 51 sites across Israel and represents the wide adaptive niche of the modern barley's ancestor. According to the genetic structure analysis, the sampled sites can be divided into seven groups, and sampled microsites located on opposing slopes or in different soil types did not show significant genetic differentiation. Although the genetic analysis indicates a simple isolation-by-distance model among the populations, examination of the genetic populations' structure with abiotic parameters in an ordination analysis revealed that the combination of elevation, mid-day temperature and rainfall explains a high proportion of the variance in the principal components analysis. Our findings demonstrate that the current populations have therefore been shaped and distinguished by non-selective forces such as migration; however, we suggest that aridity and temperature gradients played major roles as selective forces in the adaptation of wild barley in this part of the Fertile Crescent. This unique collection is a prelude for the investigation of the molecular basis underlying plant adaptation and responsiveness to harsh environments.