The biosynthesis and conjugation of indole-3-acetic acid in germinating seed and seedlings ofDalbergia dolichopetala

Germinating seed ofDalbergia dolichopetala converted both [²H₅]l-tryptophan and [²H₅]indole-3-ethanol to [²H₅]indole-3-acetic acid (IAA). Metabolism of [2-¹⁴C]IAA resulted in the production of indole-3-acetylaspartic acid (IAAsp), as well as several unidentified components, referred to as metabolites I, II, IV and V. Re-application of [¹⁴C]IAAsp to the germinating seed led to the accumulation of the polar, water-soluble compound, metabolite V, as the major metabolite, together with a small amount of IAA. Metabolites I, II and IV were not detected, nor were these compounds associated with the metabolism of [2-¹⁴C]IAA by shoots and excised cotyledons and roots from 26-d-oldD. dolichopetala seedlings. Both shoots and cotyledons converted IAA to IAAsp and metabolite V, while IAAsp was the only metabolite detected in extracts from excised roots. The available evidence indicates that inDalbergia, and other species, IAAsp may not act as a storage product that can be hydrolysed to provide the plant with a ready supply of IAA.Abbreviations HPLC-RC high-performance liquid chromatography-radiocounting - IAA indole-3-acetic acid - IAAsp indole-3-acetylaspartic acid - IAlnos 2-O-indole-3-acetyl-myo-inositol - IEt indole-3-ethanol     

Photolysis of 3-Hydroxyisoxazoles

Photolysis of 3-hydroxy-5-phenylisoxazole in methanol with a low-pressure mercury lamp afforded 5-phenyl-4-oxazolin-2-one, together with small amounts of benzoic acid and benzoylacetamide. Similarly, 3-hydroxy-5-methylisoxazole in distilled water afforded 5-methyl-4-oxazolin-2-one as the major product. Both isoxazoles were stable in sunlight for up to 20 days.     

Comparative analysis of metabolome of rice seeds at three developmental stages using a recombinant inbred line population

Plants are considered an important food and nutrition source for humans. Despite advances in plant seed metabolomics, knowledge about the genetic and molecular bases of rice seed metabolomes at different developmental stages is still limited. Here, using Zhenshan 97 (ZS97) and Minghui 63 (MH63), we performed a widely targeted metabolic profiling in seeds during grain filling, mature seeds and germinating seeds. The diversity between MH63 and ZS97 was characterized in terms of the content of metabolites and the metabolic shifting across developmental stages. Taking advantage of the ultra‐high‐density genetic map of a population of 210 recombinant inbred lines (RILs) derived from a cross between ZS97 and MH63, we identified 4681 putative metabolic quantitative trait loci (mQTLs) in seeds across the three stages. Further analysis of the mQTLs for the codetected metabolites across the three stages revealed that the genetic regulation of metabolite accumulation was closely related to developmental stage. Using in silico analyses, we characterized 35 candidate genes responsible for 30 structurally identified or annotated compounds, among which LOC_Os07g04970 and LOC_Os06g03990 were identified to be responsible for feruloylserotonin and l ‐asparagine content variation across populations, respectively. Metabolite?agronomic trait association and colocation between mQTLs and phenotypic quantitative trait loci (pQTLs) revealed the complexity of the metabolite?agronomic trait relationship and the corresponding genetic basis.     

Induction of polyphenol oxidase in germinating wheat seeds

A 50- and 100-fold increase in the o-diphenolase activity was observed respectively in excised coleoptiles and roots of wheat seedlings after germination for 4–5 days. This increased activity was associated with the appearance of several new multiple forms of o-diphenolase on acrylamide gels. The embryo-less half-seeds dissected from seedlings, however, revealed only a three-fold increase in o-diphenolase activity, without any alteration in the pattern of multiple forms. Cycloheximide substantially inhibited the activity and appearance of multiple forms of o-diphenolase, whereas actinomycin D failed to bring about a similar response. Protein synthesis was probably necessary for the formation of new multiple forms. Unlike o-diphenolase activity which was present in all parts of the seedling, the monophenolase activity was confined to the embryo-less endosperm. A 5–7-fold increase in monophenolase activity was observed in the embryo-less half-seed dissected from the seedling. A single broad band of monophenolase developed on acrylamide gels. This persisted during the early period of seed germination without addition of new multiple forms. No inhibition of monophenolase activity was observed in seeds treated with cycloheximide or actinomycin D.     

甘肃马唧山地区榆中贝母(Fritillaria yuzhongensis)的生态学特性及种子发芽规律的初步研究

榆中贝母(Fritillaria yuzhongensis)生长于马啣山的高山地带,全生育期约100 d左右,是一种生育期较短的类短命植物。在果实成熟时,种子的胚发育不全,具有后熟作用的特点,包括形态后熟和生理后热两个阶段;因此,需要一定时期的低温处理,才能完成后熟过程,以解除休眠,促使种子发芽。本试验表明:榆中贝母完成形态后熟过程的最佳温度是7℃左右,经过100d以上的低温处理才能使原胚发育成熟,继续在7℃低温下处理70d以上,才能完成生理后熟过程。榆中贝母种子休眠时间长,需要经过170d以上的低温处理,种子才能萌发。本试验结果为榆中贝母种子的萌发提出了适宜的温度范围和低温处理时间,为提高种子的出苗率和缩短栽培年限提供了科学依据。     

Protein deamidases from germinating seeds

Enzymes catalyzing the deamidation of seed storage proteins were found in germinating seeds of kidney beans ( Phaseolus vulgaris L. cv. Moldavian) and squash ( Cucurbita pepo L. cv. Mozoleevskaya). They were partially purified and characterized. The properties of these enzymes closely resemble those of the protein deamidase in germinating wheat grains. The detection of similar protein deamidases in germinating seeds of plants belonging to phytogenetically unrelated species indicates that protein deamidases are of considerable physiological significance.     

Transient expression of gus gene in intact seed embryos of Indica rice after electroporation-mediated gene delivery

Summary Two-day-old germinating intact seed embryos of Oryza sativa variety Basmati 370 were electroporated with a view to examine suitability of this system for gene delivery. The experiments were done with a plasmid having gus gene under the control of CaMV 35S promoter. Spectrofluorophotometric GUS assay revealed high activity of the introduced gene when embryos were given three electrical pulses at 1600 V cm^-1 and 100 F capacitance with a pulse length of 75 ms. Additionally, histochemical localization of GUS activity in seedlings and various organs such as leaves, coleoptiles and roots was also done. Expression of GUS activity was studied up to 15 days and found to be organ-specific, thereby showing that embryos can indeed serve as efficient recipient system. Use of cycloheximide revealed that GUS activity appears as a result of early protein synthesis after electroporation and is substantially stable in vivo.     

Differential expression of α-amylase genes in germinating rice and barley seeds

Steady-state levels of mRNA from individual -amylase genes were measured in the embryo and aleurone tissues of rice (Oryza sativa) and two varieties of barley (Hordeum vulgare L. cv. Himalaya and cv. Klages) during germination. Each member of the -amylase multigene families of rice and barley was differentially expressed in each tissue. In rice, -amylase genes displayed tissue-specific expression in which genes RAmy3B, RAmy3C, and RAmy3E were preferentially expressed in the aleurone layer, genes RAmy1A, RAmy1B and RAmy3D were expressed in both the embryo and aleurone, and genes RAmy3A and RAmy2A were not expressed in either tissue. Whenver two or more genes were expressed in any tissue, the rate of mRNA accumulation from each gene was unique. In contrast to rice, barley -amylase gene expression was not tissue-specific. Messenger RNAs encoding low- and high-pI -amylase isozymes were detectable in both the embryo and aleurone and accumulated at different rates in each tissue. In particular, peak levels of mRNA encoding high-pI -amylases always preceded those encoding low-pI -amylases. Two distinct differences in -amylase gene expression were observed between the two barley varieties. levels of high-pI -amylase mRNA peaked two days earlier in Klages embryos than in Himalaya embryos. Throughout six days of germination, Klages produced three times as much high-pI -amylase mRNA and nearly four times as much low-pI -amylase mRNA than the slower-germinating Himalaya variety.     

Ultraweak photon emission in germinating seeds: A signal of biological order

Photon emission from germinating gram seeds at various stages of growth exhibits a definite pattern. The pattern of emission changes when a seed is disrupted by physical processes, e. g. mechanical crushing, cooling or heating. The disrupted seeds do not grow. The change in the biological order responsible for seed growth and the observed changes in the pattern of photo emission suggest a link between the macroscopic spatio-temporal organization and metabolic processes.