香蕉ACC氧化酶基因(MAO3)的克隆及其表达特性分析

 根据同源扩增得到香蕉(Musa acuminata) ACC氧化酶基因(MAO3) 的核心部分, 再通过3'和5'RACE扩增上、下游序列以及Genome-Walker的方法得到启动子部分, 共获得3 718 bp长度的序列。将所得结果进行聚类分析, 发现香蕉中ACC氧化酶的氨基酸序列非常保守, 各序列间的同一性高达99% ,与单子叶植物和双子叶植物中ACC氧化酶的氨基酸序列的同源性在66.7%～71.8%之间。组织原位杂交试验表明MAO3基因的表达具有组织特异性, 初步认为是在韧皮部筛管组织中特异表达。运用实时荧光定量PCR技术, 实时监测到了MAO3基因和香蕉乙烯受体基因ERS2受机械伤诱导的定量变化。     

新型植物激素——系统素

系统素最初是指在番茄叶片中发现的与植物防卫反应相关的1种含18个氨基酸的多肽信号,现已成为植物伤害生理研究领域的热点。概述了植物系统素的结构特点、前体及其在伤信号转导中的作用等方面的研究进展,并展望了系统素今后的研究方向。     

Vascular blackening of wasabi rhizomes caused by <Emphasis Type="Italic">Pectobacterium carotovorum</Emphasis> subsp. <Emphasis Type="Italic">carotovorum</Emphasis>

Wasabi (Wasabia japonica) is grown for its highly-valued rhizome which is used as a condiment in Japanese food. Symptoms of vascular blackening in the rhizome were first observed in 2005 in plants grown in British Columbia, Canada. Microscopic observations and microbial isolation from infected tissues revealed that most of the xylem tracheid cells were blackened and bacteria were consistently associated with symptomatic plants. The bacterium most frequently recovered was identified as Pectobacterium carotovorum subsp. carotovorum (Pcc) using BioLog™ and sequencing of a specific ~510 bp IGS region. Pathogen-free plants obtained using meristem-tip micropropagation were inoculated with a wasabi isolate of Pcc. Vascular blackening symptoms developed in the rhizome after 8 weeks when the rhizome was first wounded by stabbing or cutting, or if the roots were pre-inoculated with Pythium species isolated from rhizome epidermal tissues, followed by inoculation with Pcc at 1 × 10⁸ cells ml⁻¹. Xylem tracheid cells were blackened and Pcc was reisolated from all diseased tissues. The highest frequency of rhizome vascular blackening occurred at 22°C and 27°C and these tissues occasionally succumbed to soft rot at higher temperatures, but not when inoculated tissues were incubated at 10°C. The rooting medium used by growers for vegetative propagation of wasabi was shown to contain Pcc but the pathogen was not recovered from the irrigation water. Entry of Pcc through wounds on wasabi rhizomes and the host tissue response result in symptoms of vascular blackening.     

番茄/番茄嫁接体发育过程中的过氧化物酶同工酶

分析番茄 /番茄嫁接体发育过程中的过氧化物酶同工酶 ,发现嫁接接合部酶谱和活性变化与创伤处理及对照不同。嫁接及创伤处理均可诱导同工酶产生 ,但接合部同工酶的产生往往早于创伤部位 ,有的酶带的消失情况也与创伤不同。嫁接及创伤处理前 6d ,酶活性逐渐增加 ,变化类似 ,均明显高于对照 ,随后接合部酶活性逐渐高于创伤处理 ,第 15天 ,酶活性下降且低于伤口。可见嫁接体发育过程中 ,过氧化物酶的重要作用不仅局限于伤口的愈合。对嫁接体发育和伤口愈合的关系及过氧化物酶的作用进行了讨论     

Healing process of the wounds of the branches of the Japanese persimmon that were caused by girdling,scoring, and strangulation

Girdling is widely used for many crops, mainly in order to improve the fruit set, size, and quality and to increase the yield of flower buds. However, girdling may damage trees, and permanent injury can occur if callus bridges are not formed across the ring. We determined the regeneration of vascular bundles and the healing process of wounds caused by surgical treatments. It occurred as follows: necrosis of some cell layers on the edge of the cut, callus formation and dedifferentiation of the parenchyma cells, callus proliferation, contact between callus pads, callus bridge formation, and differentiation into the mature vascular bundle; however, the innermost callus cells remained undifferentiated. At 3 days after treatment (DAT), several phloem parenchyma cell layers showed symptoms of necrosis. At 10 DAT, callus formation started in the phloem tissue below the periderm. Initially, the callus cells were uniform; however, the callus tissue pad was distinguished into 2 layers based on color and firmness. After callus bridge formation, the inner callus differentiated into the mature xylem and the outer callus, into mature phloem. In strangulation, xylem elements were formed from the inner callus pad before callus bridge formation. The callus bridge formed within 6 weeks, 20–25 days, and 14 weeks after girdling, scoring, and strangulation, respectively.     

复叶槭机械损伤后不同时间挥发物释放规律的研究

研究了复叶槭在损伤后不同时间挥发物的释放规律。结果表明:己二酸二甲酯、丁二酸二异丁酯、乙酸-3-己烯酯、6-甲基-5庚烯-2酮、蒈烯、苯骈噻唑、苯甲酸和吲哚等挥发物是复叶槭遭受机械损伤后被诱导合成的,这些物质在复叶槭中可能具有直接防御、间接防御和作为报警信号分子在植株间传递伤害信息的功能。     

Effect of wounding on cell wall hydrolase activity in tomato fruit

Changes in the activity of the cell wall hydrolases – polygalacturonase (EC 3.2.1.15), pectinesterase (EC 3.2.1.11) and β-galactosidase (EC 3.2.1.23) – have been investigated following wounding of tomato fruit pericarp tissue (Lycopersicon esculentum cv. Ailsa Craig). In ripening fruit wounding appears to arrest the further synthesis of polygalacturonase. β-Galactosidase synthesis may also have been arrested in ripening fruit. The level of pectinesterase declined over the first 24 h following harvest, and since this was apparent in both wounded and unwounded tissue may be related to a harvest, rather than a wounding effect. There was a recovery of activity in intact fruit by 48 h after harvest but this seems to be impaired in wounded tissue. In the case of pectinesterase, this observation was extended to examine the changes in isoform profile and it appeared that the decline of this enzyme may be associated with the reduction of one specific isoform — PE2. In contrast to ripening fruit, wounding of fruit at the fully ripe stage appears to have no significant effects on the activities of any of these three enzymes.     

Early recognition of graft compatibility in <Emphasis Type="Italic">Uapaca kirkiana</Emphasis> Müell Arg. clones,provenances and species

Examination of callus micro-grafts in Uapaca kirkiana Müell Arg. was carried out with the objective of determining early signs of graft compatibility. Leaves from U. kirkiana, U. nitida and Jatropha curcas trees were used for callus induction. Two pieces of callus were co-cultured on Murashige and Skoog (MS) medium with different supplements. Co-cultured calli were embedded in paraffin wax and dissected. The specimens were stained in safranin and fast green before viewing under a light microscope. Results showed that MS medium with 0.1 mg l⁻¹ thidiazuron (TDZ) and 0.5 mg l⁻¹ naphthaleneacetic acid (NAA) or 1.0 mg l⁻¹ dichlorophenoxyacetic acid (2,4-D) and 0.5 mg l⁻¹ NAA was effective for callus induction. There were no necrotic layers at the unions within U. kirkiana clones and provenances, but a differential growth (irregularity) between U. kirkiana and U. nitida co-cultured calli. Phenol deposits were observed at the union interfaces of U. kirkiana combinations and were high on calli derived from mature trees. Phenol deposits were absent at the union of J. curcas heterografts. Necrotic layers developed at the unions of U. kirkiana and J. curcas micro-grafts and indicating an outright graft incompatibility. Accumulation of phenol deposits at the union interfaces inhibited graft compatibility in many U. kirkiana combinations. Callus fusion technique can be used to identify partners with an outright graft incompatibility, especially for distant related plant species.     

Wounding of melon fruits as a model system to study rind netting

The rind of muskmelon (Cucumis melo L. var. reticulatus) fruits contains a network of suberized periderm tissue, referred as the ‘net’, which originates in response to cracking of the fruit surface during its enlargement. Shallow cuts were made on the surface of melons to mimic naturally occurring cracking and induce net-like periderm development. Histological analysis of wounded fruits of the climacteric netted variety Krimka, and of two smooth melon varieties: the climacteric Momordica and the non-climacteric Tamdew, indicated that smooth melon varieties can undergo netting when their rind is fissured. Furthermore, the results implied that the climacteric character is not essential for net-tissue development, even though most netted varieties are climacteric. The involvement of ethylene in net-like periderm development was studied by analyzing the expression pattern of the ethylene-biosynthesis genes 1-aminocyclopropane-1-carboxylate synthase 1 and 1-aminocyclopropane-1-carboxylate oxidase 1 following wounding and during periderm development, and by applying the ethylene-generating chemical, Ethrel, as a lanolin paste, on the fresh cuts. Results suggested ethylene involvement in periderm initiation, but continuous exposure may interfere with further tissue development and organization. General implications of the current study on periderm development are further discussed.     

植物系统素研究进展

概述植物系统素的结构特点,综述系统素原、系统素的膜受体、系统素在伤信号转导中的作用等研究进展,展望系统素今后的研究方向。