SUMO化修饰系统在哺乳动物胚胎发育及器官发生中的作用

小分子泛素相关修饰物蛋白（small ubiquitin-related modifier protein,SUMO）化修饰是一种广泛存在的蛋白质翻译后修饰形式,存在于动物多个生理和病理过程中,并涉及复杂的信号通路调节过程,是细胞对应激反应的重要调节机制,并且越来越多的研究表明,SUMO化修饰在哺乳动物胚胎发育及器官发生过程中发挥重要作用。在胎儿发育过程中,SUMO化对于器官的形成及发育起着至关重要的作用。SUMO化途径的各组成成分（UBC9、SUMO1～3、PIAS、SENP1～7）在胚胎发育过程中协调胚泡与子宫间的对话、心脏发育以及颅面发育中都发挥着重要作用。在发育过程中SUMO化修饰一旦失调,则可能导致胚胎植入前缺陷、胚胎发育缺陷以及胚胎致死。本综述总结了SUMO化修饰的分子机制,以及SUMO化途径各个组成成分（SUMO、UBC9、PIAS、SENPs）在早期胚胎发育及后续器官发生中功能的最新进展,以望为后续的研究提供借鉴。     

Propagation in vitro of the apple rootstock M4: effect of phytohormones on shoot quality

The quality of shoots in cultures of the apple rootstock, M4, was used as a criterion for the selection of an optimum medium. The frequency of shoots in defined shoot clases was monitored for each of five media, which differed in the type and concentration of phytohormone. Media containing BA (1.15 mg l^-1) and IBA (either 0.15 or 0.20 mg l^-1) produced the maximum number of shoots that were desirable for transplantation and acclimatization.     

Bialaphos stimulates shoot regeneration from hairy roots of snapdragon (Antirrhinum majus L.) transformed by Agrobacterium rhizogenes

Hairy roots of snapdragon (Antirrhinum ma-jus L.: Scrophulariaceae) induced by a wild-type strain of Agrobacterium rhizogenes were cultured on media containing various concentrations of a phosphinothricin-based herbicide, bialaphos, or plant growth regulators (PGRs). Adventitious shoot regeneration from hairy roots was observed with a low frequency (10%) on half-strength Murashige and Skoog medium. Addition of α-naphthalene-acetic acid in combination with 6-benzylaminopurine, thidiazuron, or zeatin to the medium had no effect on shoot regeneration from hairy roots. Although bialaphos at 0.9 mg l^–1 or more was toxic to hairy roots, it significantly increased the shoot regeneration frequency up to 56% at 0.5 mg l^–1. In contrast, non-transformed roots and leaves regenerated no shoots on media with or without bialaphos. Regenerated shoots detached from host roots readily developed roots on gellan-gum-solidified medium. Regenerated plants were successfully transferred to the greenhouse, but did not produce seed. Received: 24 February 1997 / Revision received: 10 July 1997 / Accepted: 28 July 1997     

Distribution of NO3− reduction between roots and shoots of peachtree seedlings as affected by NO3− uptake rate

The distribution of NO₃^? reduction between roots and shoots was studied in hydro-ponically-grown peach-tree seedlings (Prunus persica L.) during recovery from N starvation. Uptake, translocation and reduction of NO₃^?, together with transport through xylem and phloem of the newly reduced N were estimated, using ¹⁵N labellings, in intact plants supplied for 90 h with 0.5 mM NH₄⁺ and 0.5, 1.5 or 10 mM NO₃^?. Xylem transport of NO₃^? was further investigated by xylem sap analysis in a similar experiment. The roots were the main site of NO₃^? reduction at all 3 levels of NO₃^? nutrition. However, the contribution of the shoots to the whole plant NO₃^? reduction increased with increasing external NO₃^? availability. This contribution was estimated to be 20, 23 and 42% of the total assimilation at 0.5, 1.5 and 10 mM NO₃^?, respectively. Both ¹⁵N results and xylem sap analysis confirmed that this trend was due to an enhancement of NO₃^? translocation from roots to shoots. It is proposed that the lack of NO₃^? export to the shoots at low NO₃^? uptake rate resulted from a competition between NO₃^? reduction in the root epidermis/cortex and NO₃^? diffusion to the stele. On the other hand, net xylem transport of newly reduced N was very efficient since ca 70% of the amino acids synthesized in the roots were translocated to the shoots, regardless of the level of NO₃^? nutrition. This net xylem transport by far exceeded the net downward phloem transport of the reduced N assimilated in shoots. As a consequence, the reduced N resulting from NO₃^? assimilation, principally occurring in the roots, was mainly incorporated in the shoots.     

PLASTOCHRON3/GOLIATH encodes a glutamate carboxypeptidase required for proper development in rice

Most aerial parts of the plant body are products of the continuous activity of the shoot apical meristem (SAM). Leaves are the major component of the aerial plant body, and their temporal and spatial distribution mainly determines shoot architecture. Here we report the identification of the rice gene PLASTOCHRON3 ( PLA3 )/ GOLIATH ( GO ) that regulates various developmental processes including the rate of leaf initiation (the plastochron). PLA3 / GO encodes a glutamate carboxypeptidase, which is thought to catabolize small acidic peptides and produce small signaling molecules. pla3 exhibits similar phenotypes to pla1 and pla2 – a shortened plastochron, precocious leaf maturation and rachis branch-to-shoot conversion in the reproductive phase. However, in contrast to pla1 and pla2 , pla3 showed pleiotropic phenotypes including enlarged embryo, seed vivipary, defects in SAM maintenance and aberrant leaf morphology. Consistent with these pleiotropic phenotypes, PLA3 is expressed in the whole plant body, and is involved in plant hormone homeostasis. Double mutant analysis revealed that PLA1 , PLA2 and PLA3 are regulated independently but function redundantly. Our results suggest that PLA3 modulates various signaling pathways associated with a number of developmental processes.     

Peroxidase and catalase changes during in vitro adventitious shoot organogenesis from hypocotyls of Albizia odoratissima L.f. (Benth)

Hypocotyls of Albizia odoratissima cultured on shoot induction medium (MS medium with 7.5 μM BAP and 0.5 μM NAA) showed adventitious shoot organogenesis under light with 16 h photoperiod. Similar cultures under total darkness produced non-morphogenic calli. The changes in the specific peroxidase and catalase activity, total protein content and acidic isoperoxidase pattern were compared between the culture showing shoot organogenesis and culture producing non-morphogenic calli. It was found that in vitro shoot bud differentiation is accompanied by an increase of the specific activities of peroxidase and catalase in culture kept under light. In parallel with the above changes the total protein content reached to the maximum level and also a new isoperoxidase (P10) expressed on the 21st day in cultures kept under light. Conversely, culture producing non-morphogenic calli underwent a reverse change in specific peroxidase activity. This change in antioxidant enzyme activities corresponds to the histological observation of shoot bud differentiation in cultures kept under light.     

Direct shoot bud induction and plant regeneration in <Emphasis Type="Italic">Capsicum frutescens</Emphasis> Mill.: influence of polyamines and polarity

Direct shoot bud induction and plant regeneration was achieved in Capsicum frutescens var. KTOC. Aseptically grown seedling explants devoid of roots, apical meristem and cotyledons were inoculated in an inverted position in medium comprising of Murashige and Skoog (Physiol Plant 15:472–497, 1962) basal medium supplemented with 2-(N-morpholine) ethanesulphonic acid buffer along with 2.28 μM indole-3-acetic acid, 10 μM silver nitrate and either of 13.31–89.77 μM benzyl adenine (BA), 9.29–23.23 μM kinetin, 0.91–9.12 μM zeatin, 2.46–9.84 μM 2-isopentenyl adenine. Profuse shoot bud induction was observed only in explants grown on a media supplemented with BA (26.63 μM) as a cytokinin source and 19.4 ± 4.2 shoot buds per explant was obtained in inverted mode under continuous light. Incorporation of polyamine inhibitors in the culture medium completely inhibited shoothoot bud induction. Incorporation of exogenous polyamines improved the induction of shoot buds under 24 h photoperiod. These buds were elongated in MS medium containing 2.8 μM gibberellic acid. Transfer of these shoots to hormone-free MS medium resulted in rooting and rooted plants were transferred to fields. This protocol can be efficiently used for mass propagation and presumably also for regeneration of genetically transformed C. frutescens.     

The nature of plant growth-promoting effects of a pseudoalteromonad associated with the marine algae Laminaria japonica and linked to catalase excretion

AIMS: The goal of this study was to identify a marine algae-associated bacterium isolated from Laminaria japonica and investigate this microorganism's growth-promoting effects on plants. METHODS AND RESULTS: The bacterium, identified as Pseudoalteromonas porphyrae, was determined to display a biostimulatory activity for seed germination and shoot growth in several agricultural plants and also for growth in ginseng callus cell culture. This biostimulatory activity was linked to a catalase enzyme that was excreted in the maximal amount during the transition from logarithmic growth phase to stationary growth phase. In addition, selected shifts in growth temperature and medium salinity affected the amount of enzyme excreted. The purified catalase was determined to be composed of identical subunits. The catalase of interest displayed significantly higher biostimulatory activity than the catalase from bovine liver. CONCLUSIONS: The catalase investigated in this study is unique in that it promotes growth in and possibly contributes to stress tolerance of plants. SIGNIFICANCE AND IMPACT OF THE STUDY: The catalase of interest has the potential for use in treatments that aim to improve percent seed germination as well as obtaining tall shoots in a shorter time period.     

Dose-, time-, and tissue-dependent effects of 5-bromo-2′ -deoxyuridine on the in-vitro organogenesis of Arabidopsis thaliana

Vigorous organogenesis can be induced from hypocotyl and root explants of Arabidopsis thaliana using a two-step culture procedure consisting of preculture on callus-inducing medium (CIM) and subsequent culture on shoot-inducing medium (SIM) or root-inducing medium (RIM). With this culture system, we examined the influence of 5-bromo-2′-deoxyuridine (BrdU), a thymidine (dT) analogue, on plant organogenesis in vitro. Treatment with BrdU during SIM or RIM culture had negative effects on shoot and root redifferentiation over a broad range of concentrations. When explants were exposed to low concentrations of BrdU during preculture and then transferred onto BrdU-free SIM, shoot redifferentiation was accelerated significantly. At higher doses, BrdU treatment during the pre-culture inhibited shoot redifferentiation strongly in hypocotyl explants, but not in root explants. This suggests that a target of the BrdU action lies within the process of acquisition of cell proliferation competence specifically involved in hypocotyl dedifferentiation. These effects of BrdU were counteracted by the simultaneous addition of excess dT. BrdU-pretreated and untreated explants did not differ significantly in the phytohormone dependency of shoot redifferentiation. Our results provide a basis for future studies on plant organogenesis combining pharmacological analysis with BrdU as a probe and molecular genetics with Arabidopsis mutants.