STUDIES OF SPERMATOGENESIS IN THE HEPATICAE V. BLEPHAROPLAST DEVELOPMENT IN MARCHANTIA POLYMORPHA

Coaxial centrioles and a microtubule organizing center (MTOC) constitute each centrosome in spermatid mother cells of Marchantia polymorpha. During cell division the centrosome separates at its midregion and the two centrioles undergo a planar rotation that brings them to lie somewhat staggered and nearly parallel with their proximal ends embedded in osmiophilic granular material similar in appearance to that of the MTOC. Microtubules of the multilayered structure (MLS) arise in this material below the posterior centriole and parallel to its long axis. The rotation of centrioles and the initiation of S₁ tubules below the posterior centriole determine polarity of the incipient blepharoplast. Lower MLS strata are formed under the anterior centriole by the compaction of granular, osmiophilic matrix. Formation and growth of S₂ vertical lamellae occur at the left front edge of the MLS in association with MTOC-like matrix localized near the cell membrane. The MLS enlarges to about 0.4 μm wide by 0.6 μm long and is ovoid in outline except for a short distal projection underlying the posterior centriole. Subsequently the lamellae are transformed into homogenous, osmiophilic matrix that contributes directly to the expansion of all MLS strata including microtubules. The stratum of lamellae is interpreted as a planar MTOC subject to morphogenetic control. Each of the four strata grows proximally while the tapering distal projection lengthens beneath the posterior basal body. Dense matrix above the MLS, apparently elaborated by the S₂ layer, is organized into cartwheel and triplet components of the basal bodies’ proximal extensions. Organization of triplet tubules proceeds from proximal to distal toward preexisting triplets. Osmiophilic matrix contributes to the formation of microtubule keels and osmiophilic crests and may serve as a cementing material that stabilizes the spatial relationships of blepharoplast components. After full expansion of the MLS’ lower strata, the S₂ layer is reorganized into lamellae. Flagellar growth in Marchantia is postulated to involve a process whereby subunits or their precursors are elaborated by the MLS, translocated to the distal end of the flagellum and incorporated into the axonemal tubules. When MLS microtubules elongate to form a long, narrow band, the distal half of the S₂ layer is again in the osmiophilic matrix state.     

THE FINE STRUCTURE OF OOGENESIS IN MARCHANTIA POLYMORPHA

Archegonium development, beginning with the archegonial initial and culminating in the mature egg, was studied with the electron microscope. The ultrastructural features of the beginning stages in development of the archegonium are relatively similar to one another. Plasmodesmata occur between all adjacent cells at this time. After the secondary central cell is formed these protoplasmic connections are lost, and both axial and parietal cell lineages begin to show signs of ultrastructural differentiation. The mature egg is characterized by cytoplasm rich in ribosomes and larger organelles. Mitochondria and simplified plastids commonly display a juxtaposed association. As far as could be ascertained the numerous plastids and mitochondria in the egg of Marchantia arise through division of preexisting organelles and are not formed anew from evaginations of the nucleus. Blebbing of the nucleus produces polymorphic organelles which appear to be pinched off into the cytoplasm. The mature egg also contains vacuoles and lipid bodies toward its periphery, while dictyosomes and extensive endoplasmic reticulum occur throughout. The space between the wall cells and the mature egg appears to contain an amorphous substance. No extra membrane was observed around the mature egg.     

EFFECTS OF EXOGENOUS AMINO ACIDS ON THE DEVELOPMENT OF MARCHANTIA POLYMORPHA GEMMALINGS

The effects of various nitrogenous compounds in concentrations ranging from 10^-4 to 10^-3 m on the growth and morphology of gemmae of Marchantia polymorpha L. were investigated under axenic conditions. Only nine of the 24 compounds tested were effective in altering the normal developmental pattern of this plant. l -Isoleucine, l -leucine, l -methionine or l -threonine resulted in a disruption of the apical regions at concentrations of 10^-3 m . The addition of lower concentrations of l -arginine, l -histidine, l -hydroxyproline, l -lysine or l -tryptophan to the nutrient medium resulted in morphological irregularities. These latter abnormal growth patterns were highly specific for the individual amino acids and ranged from lack of air chamber development to complete thallus disorganization. Both the formation and duration of abnormal developmental patterns were dependent upon the concentration of the amino acids employed. Although the experimental results are inconsistent with certain physiological mechanisms such as a general nitrogen toxicity, alternative possibilities are discussed.     

BIOCHEMICAL CHANGES DURING SEXUAL DEVELOPMENT IN MARCHANTIA POLYMORPHA: I. ESTERASES

Extracts of uninduced thalli, induced thalli, stalks, antheridiophore and archegoniophore disks of Marchantia polymorpha were subjected to starch-gel zone electrophoresis. Developed gels were treated with appropriate reaction mixtures to detect sites of activity for 12 enzyme systems; only phosphatases, esterases, and peroxidases were observed. Although common sites of phosphatase, peroxidase, and esterase activity were detected in all tested extracts, additional sites of peroxidase and esterase activity were found in extracts from antheridiophore disks. The antheridia provided the additional esterases as determined by the electrophoresis of antheridial extracts and by a histochemical test for esterases in sections of antheridiophores.     

POLARITY AND LOCALIZATION OF AUXIN MOVEMENT IN THE HEPATIC,MARCHANTIA POLYMORPHA

Transport of ¹¹C-indoleacetic acid in thallus explants of Marchantia polymorpha was basipetal and localized in midrib tissue. Transport was inhibited by aging, 2,3,5-triiodobenzoic acid, cinnamic acid, and ethylene. Similarities between these responses and auxin transport in higher plants are considered and morphogenetic potential of the phenomenon in Marchantia identified.     

VARIATION IN A POLYPLOID,DIOICOUS LIVERWORT,MARCHANTIA GLOBOSA

This study was undertaken in order to determine the population structure in a tropical, geographically isolated liverwort, Marchantia globosa Brid. ex Web., a thallose species endemic to the Mascarenes and Comoro Islands. A survey of numerous populations on Réunion showed M. globosa to be ecologically tolerant and morphologically quite variable. The morphological differences between populations could only be explained by a size effect, due principally to altitude. Neither cytological nor electrophoretic analyses revealed any genetic basis for distinguishing subpopulations. In spite of an apparently high reproductive effort, sexual structures being produced abundantly, few spores reach maturity. No electrophoretically detectable genetic polymorphism was found. Morphological variation appears to result from phenotypic plasticity.     

SPORE DEVELOPMENT IN THE LIVERWORT RICCARDIA PINGUIS

The ontogeny of spores of the liverwort Riccardia pinguis was studied at the light and electron microscope levels. Three stages of development were arbitrarily defined: spore mother cell (SMC); early tetrad with nonpigmented and unsculptured walls; and mature tetrad with pigmented and sculptured spore walls. The SMC is quadrilobed with a two-layered SMC wall, containing a central nucleus, many chloroplasts, spherosomes, and other organelles. During and following meiosis cell plates form from coalescing Golgi vesicles. These plates by continued coalescence eventually form a septum, completing the tetrad. This septum comprises middle lamella and primexine; within the latter the exine forms. By continued addition of vesicle contents to the septum and dorsal surfaces of the tetrad, the exine (sexine and nexine) and intine layers of the spore wall are laid down. The contents of the vesicles change successively during wall formation, corresponding to the different wall layers being formed. It is concluded that wall formation is under the exclusive control of the spore protoplast, and that the pattern of the mature exine is determined by the primexine. Rearrangement of organelles and other cellular components during sporogenesis is described.     

APICAL DOMINANCE,POLARITY, AND ADVENTITIOUS GROWTH IN MARCHANTIA POLYMORPHA

Benzylaminopurine, indoleacetic acid, and the auxin inhibitors transcinnamic acid, triiodobenzoic acid, and dinitrophenol were employed to elucidate the role of apical dominance and hormones during regeneration of thalli and gemmae of Marchantia polymorpha L. The cytokinin suppressed normal gemma germination and led to the development of nodular, callus-like growths. When removed from the influence of benzylaminopurine, the site and magnitude of normal thallus outgrowths varied with the length of time that the tissue had remained on the cytokinin-containing medium. This aberrant germination was not influenced by the incorporation of indoleacetic acid into the medium. Exogenous auxin neither accelerated nor inhibited the regeneration of normal thallus growth on excised vegetative discs. Transcinnamic acid and dinitrophenol inhibited regeneration. Auxin reversed this suppression. Triiodobenzoic acid did not significantly affect regeneration. Autoradiographs demonstrated a pronounced accumulation of labelled auxin in the midribs and the acropetal regions of excised thallus discs. This evidence suggests that there is an endogenous, basipetal auxin gradient in Marchantia; that the maintenance of this gradient is vital to normal growth and regeneration of the thallus; and that high endogenous concentrations of cytokinin destroy this polarity by increasing the auxin-synthesizing capacity of the tissue.     

地钱在离体条件下的无性繁殖及脱分化与再分化的研究

地钱(Marchantia polymorpha L.)的胞芽和配子体先在 MS 培养基上补加1mg/l 2,4-D和3%蔗糖,经过启动部分脱分化后,再移入1/2KNOP 培养基补加4—8mg/l 2,4-D,0.25～0.5mg/l BA 与 MS 的铁盐,20g 蔗糖,此后愈伤组织肉眼可见,但仍伴有假根。最后移入 White 培养基添加丙酮酸、延胡索酸与柠檬酸三者混合物(5mmol/l)及1mg/l 2,4-D与4%葡萄糖后,始呈现彻底的脱分化状态,愈伤组织才能正常生长。整个脱分化时间长达10个月。而再分化成配子体却比高等植物容易,甚至移入不含激素的 MS 基本培养基即可形成正常的配子体。     

香港地钱抗菌化学成分研究

利用生物活性试验和^1H NMR追踪，从香港地钱（Marchantia paleacea Bertol)的乙醇提取物中简单快速分离具有抗菌活性的三个已知芳香化合物：2－羟基－3，7－二甲氧基菲（1），marchantin C(2)和isoriccardin C(3)。化合物（1）的NMR测定以及晶体结构对文献值部分NMR数据进行了修正。     

BIOCHEMICAL CHANGES IN RAT BRAIN ASSOCIATED WITH THE DEVELOPMENT OF THE BLOOD-BRAIN BARRIER

—Subcellular fractions from brains of 5, 10, 13, 16, 21, 30 day-old and adult rats were prepared. Protein content and various enzyme activities were assayed in all fractions and brain homogenates. γ-Glutamyl transpeptidase activity and 5′-nucleotidase were very low at 5 days of life but steadily increased, reaching adult concentrations at about 30 days after birth. Alkaline phosphatase, instead slowly decreased with maturation, while monoamine oxidase after an initial decrease, increased rapidly to adult levels. The relation between the appearance of enzymatic activity in brain and the blood-brain barrier function is discussed.     

INHIBITION OF THE BIOSYNTHESIS OF ISOPRENOID COMPOUNDS BY PHENOLIC ACIDS IN THE RAT BRAIN

—The incorporation of [2-¹⁴C]mevalonate into nonsaponifiable lipids by rat brain homogenates is inhibited by phenolic acids derived from tyrosine. The phenyl acids derived from phenylalanine are inhibitory only at very high concentrations compared with phenolic acids. The brain is more sensitive to inhibition by the phenolic acids than the liver. These studies indicate a possible role for phenolic acids in the impairment of cerebral sterol metabolism in phenylketonuria.     

HYDROXYPROLINE-INDUCED CHANGES IN FORM,APICAL DEVELOPMENT,AND CELL WALL PROTEIN IN THE LIVERWORT PLAGIOCHILA ARCTICA

Hydroxy-L-proline induces phenovariation in Plagiochila arctica Bryhn & Kaal. (Plagiochilaceae) similar to that previously induced by this compound in representatives of three other families of leafy liverworts (i.e., Cephaloziaceae, Jungermanniaceae and Scapaniaceae). Because the pattern of phenovariation in P. arctica was uniform and persistent over relatively long incubation periods, adequate material for chemical analysis and reliable material for histological analysis could be obtained for the first time. These analyses revealed interesting correlations between form, cellular “behavior,” and wall chemistry in normal and phenovariant plants. The correlations interpreted in the context of available information suggest, as a working hypothesis, that hydroxyproline-proteins regulate several aspects of morphogenesis in leafy liverworts by suppressing growth and development at critical times in highly localized areas.     

水稻胚胎发育过程相关基因的鉴定(简报)

为了研究水稻胚胎发育的分子机制,我们运用抑制差减杂交(SSH)技术鉴定了胚胎发育早期(授粉后5-7天)和晚期(授粉后15-17天)优势表达的基因.结果发现在胚胎发育早期和晚期优势表达的表达序列标签(EST)分别为47个和15个,这些EST可分为新陈代谢、蛋白合成、蛋白修饰、细胞防御或胁迫、转运运输、转译、DNA或RNA结合等多种类别.其中有32%的EST在GenBank的生物信息数据库中没有同源序列.从两个SSH文库中随机抽取11个EST分别在5DAP和15DAP水稻分化的胚胎中进行RT-PCR验证.结果显示SSH文库所获得的EST符合建库要求.对这些EST所代表的基因作进一步研究将有助于了解其在水稻胚胎发育中的生物学功能.     

INDUCED APOSPORY IN THE LIVERWORT BLASIA PUSILLA

Immature sporophytes of Blasia pusilla L. collected in the field were excised from the protective gametophytic tissues and cultured on a slightly modified Knop's agar substrate in microphytotrons. Under the experimental conditions the setae elongated and after 33½ to 6 weeks many began to give rise to from 1 to 20 or more aposporous outgrowths. These subsequently developed into young gametophytes. The apices were then cut off, sterilized, and grown on glucose-mineral agar in aseptic culture. The resulting gametophytes were similar to haploid plants derived from spores in pattern and rate of growth, and in possession of rhizoids, ventral scales, lateral lobes, auricles, and stellate and discoid gemmae. They produced archegonia but no antheridia. The chromosome number of the aposporous plants was 18 in contrast to the normal haploid number of 9.