Characterization of β-amylase and its deficiency in various rice cultivars

 β-Amylase deficiency in various cultivars of rice was examined at the molecular level. Using an antibody against β-amylase purified from germinating seeds of rice, we were able to demonstrate the expression and organization of the β-amylase gene in normal and deficient cultivars. Although β-amylase is a starch-hydrolyzing enzyme, as is α-amylase, the β-amylase protein/gene is expressed differently from the α-amylase protein/gene; i.e. (1) β-amylase is synthesized only in aleurone cells, (2) the enzyme production in the embryo-less half-seeds is not under hormonal control. We identified some cultivars of rice that are deficient for β-amylase activity. We present new evidence that synthesis is blocked at the level of mRNA synthesis in the deficient cultivars. The usefulness of β-amylase as a crop trait is also discussed. Received: 8 May 1998 / Accepted: 5 June 1998     

The structure of 180° supernumerary limbs and a hypothesis of their formation

The results of a detailed analysis of 100 supernumerary limbs generated by 180° ipsilateral rotation (on the same limb stump) of regeneration blastemas is presented. The limbs were analyzed in terms of their position of origin, frequency, cartilage structure by Victoria blue staining, and muscle structure by serial sections. Single, double, or triple supernumeraries can be produced at no unique position of origin, although the posterodorsal quadrant was preferred. Four classes of supernumerary limbs were generated by such operations—normal; double dorsal or double ventral; part normal/part mirror imaged; part normal/part inverted in approximately equal frequencies. After amputation of these supernumeraries the same muscle patterns are faithfully regenerated. A hypothesis to explain the production of these abnormal limbs is proposed based on the observed phenomenon of fusion of supernumerary blastemata, but their regenerative behaviour presents problems for current models of pattern formation. Similar results have been obtained with developing limb buds and the relation between development and regeneration is discussed.     

Supply and partitioning of assimilates to roots of Medicago sativa L. and Lotus corniculatus L. under anoxia

Abstract A current explanation of the mechanism of flooding injury to roots suggests that oxygen deficiency depresses the supply of respirable carbohydrates sufficiently to inhibit fermentation. However, even though it has been shown that phloem transport of assimilate is sharply reduced to anaerobic roots, inhibition of assimilate metabolism has also been suggested to be an important factor. This study examines these hypotheses by relating assimilate supply and metabolic activity in anoxic roots of alfalfa (Medicago sativa L.), a flood-intolerant species, and birdsfoot trefoil (Lotus corniculatus L.), a flood-tolerant plant. Roots were made anoxic (severe O₂ deficiency) for 2, 4 or 6 d and shoots were labelled with ¹⁴CO₂. Assimilate transport to the roots and metabolism to structural components were significantly decreased in both species in response to anoxia. Trefoil exhibited significantly greater ¹⁴C incorporation into the residue fraction at 4 d anoxia than did alfalfa, and this was consistent with the greater flooding tolerance of trefoil. When assimilate supply to O₂-deficient roots was decreased by shoot shading, shoot fresh weight was reduced by both anoxia and light treatments. Root-soluble sugars were significantly decreased by shading but were greatly increased in response to anoxia. Root starch concentration also increased under anoxia. Root K⁺ concentration was reduced by anoxia only. The energy status (ATP/ADP) of roots was significantly decreased by shading; however, anoxia reduced the energy status only in unshaded plants. The data indicate that carbohydrate supply to anaerobic roots does not appear to be a limiting factor in the metabolic response of alfalfa roots. Alternatively, metabolism of assimilate in anoxic roots may be an important determinant of survival.     

水稻原生质体产生细胞团的冰冻保存和冻后再生植株形成

水稻(Oryza sativa L.)原生质体产生的细胞团加上10-20％的二甲亚枫(DMSO)和10-20％的蔗糖,置于液氮中保存。冻后细胞生存率达到对照的40-50％。存活的细胞在附加2×10~(-5)mol/l 2,4-D 的Linsmier-Skoog(Ls)固体培养基上再生长,然后将形成的愈伤组织块转到附加10~(-6)mol/l NAA,4×10~(-6)mol/l 激动素和10~(-6)mol/l 2 IP 及8％的蔗糖的 LS培养基上分化出芽并形成植株。     

Chromophore structure in phytochrome intermediates and bleached forms of phytochrome

Phytochrome (120 kdalton or 60 kdalton) was isolated from etiolated seedlings of Avena sativa L. cv. Pirol (Baywa München). Irradiation with red light of the P_r form at −23°C in aqueous medium or at −40°C in 66% glycerol leads to the intermediate meta-Rb. Acidification of the glycerol solution at −40°C leads to the absorption of the 15(E) phytochrome chromophore (= P_fr chromophore). Subsequent irradiation transforms this into the 15(Z) chromophore (= P_r chromophore). The presence of the 15(E) chromophore was demonstrated by the same methods also in phytochrome bleached either as P_fr in the dark by 4 M urea, methanol, acetone, ethylene glycol, 8-anilinonaphthalene-1-sulfonate, or as P_r by irradiation with red light in the presence of the same agents. Phytochrome bleached by sodium dodecylsulfate or by dehydration was also investigated. It was concluded that bleached phytochrome contains the P_fr chromophore without specific interaction with the protein.     

Linkage analysis for 18 enzyme loci in Pinus rigida Mill.

Summary Estimates of recombination frequency among enzyme loci of pitch pine revealed two new linkages, Mdh3:Pgm2 (=0.01) and Pep1:Mdh4 (=0.38), and confirmed two previously established linkages. Tighter linkage (=0.30) was ruled out for nearly all gene pairs examined. In general, the Bayesian approach used in this study to test for linkage performed better than alternative methods.This work was supported by the School of Natural Resources, College of Agricultural and Life Sciences, University of Wisconsin, Madison, WI, and by McIntyre-Stennis, project no. 142-C385     

The effect of vitamin A on limb regeneration in Rana temporaria

Previous experiments in which vitamin A has been administered to developing or regenerating limbs have shown that different limb axes are affected. In regenerating axolotl limbs, serial reduplications in the proximodistal axis are produced. In the developing chick limb bud, mirror-imaged reduplications in the anteroposterior axis are produced. Results reported here on Rana temporaria limb buds reveal that vitamin A causes both effects to occur. That is, limbs are both serially reduplicated in the proximodistal axis and mirror imaged in the anteroposterior axis. Time and concentration effects are explored and the significance of these results for our current understanding of axial organisation in limbs is discussed.     

水稻、小麦、油菜和烟草细胞质雄性不育系统中组分Ⅰ蛋白的比较分析

组分Ⅰ蛋白(RuBP羧化酶/加氧酶)的生物合成系由叶绿体基因和细胞核基因共同控制,所以,被作为研究细胞质遗传的标记。本实验用免疫化学和氨基酸成分分析等方法,对水稻(珍汕97)、小麦(繁7)、油菜(湘矮早)和烟草(G28)的细胞质雄性不育系及其保持系的组分Ⅰ蛋白作了比较,同时对不同作物的组分Ⅰ蛋白也作了免疫鉴定。结果表明,细胞质雄性不育系及其保持系的组分Ⅰ蛋白差异不大,但是,四种不同作物的组分Ⅰ蛋白之间有明显差异。