Influence of Abscisic Acid and the Abscisic Acid Biosynthesis Inhibitor, Norflurazon, on Interactions Between Phytophthora sojae and Soybean (Glycine max)

A comparison was made of the effects of abscisic acid (ABA) and the ABA biosynthesis inhibitor, norflurazon on the interaction between soybean leaves and Phytophthora sojae. Inoculation of leaves of cv. Harosoy resulted in a compatible interaction typified by the presence of spreading, water soaked lesions with ill-defined margins while inoculation of cv. Haro 1272 resulted in an incompatible interaction with lesions restricted to the inoculation site. Activity of phenylalanine ammonia lyase (PAL) slowly increased in the compatible interaction but in the incompatible interaction there was a rapid rise in activity within 8h after inoculation. When Haro 1272 plants were treated with ABA the normally incompatible interaction with race 1 was changed to what resembled a compatible interaction and activity of PAL was reduced to control levels. There was no visible effect on the compatible combination. In contrast when plants of cv. Harosoy were treated with norflurazon the normally compatible interaction with race 1 was changed to that which resembled an incompatible interaction and PAL activity increased to high levels rapidly. There was no effect of norflurazon on the incompatible interaction of cv. Haro 1272 with race 1. Stomata on leaves of cv. Harosoy treated with norflurazon closed within 2h of inoculation resembling the response of stomata in normal incompatible interactions but not compatible interactions where stomata remained open. On leaves of cv. Harosoy treated with norflurazon at sites 3 and 20mm from the inoculation point stomata also closed. These results extend and confirm the idea that ABA is a molecule that may regulate the outcome of the interaction between soybeans and P. sojae.     

Some compatible Rhizobium leguminosarum strains in peas decrease infections when parasitised by Orobanche crenata

Orobanche crenata (crenate broomrape) produces serious damage to many legume crops and particularly becomes a limiting factor for pea production in the Mediterranean basin. Nodulation effects on pea–broomrape relationships were studied using the commercial pea cultivar Douce de Provence and different Rhizobium strains using pot and Petri dish experiments. First, the benefit of bacterial inoculation on plant growth and efficiency of N incorporation were demonstrated for two isolates, P.SOM and P.1236. These isolates did not influence parasite germination induced by the artificial stimulant, GR24. In contrast, pea root inoculation with P.SOM and P.1236 isolates led to a reduced root infection by O. crenata , resulting from a lower Orobanche germination rate close to pea roots and a limited capacity of the parasitic seedlings to develop tubercles. Broomrape necrosis was observed both before and after parasite attachment to inoculated pea roots. Concomitantly, reduction in infection was accompanied by enhanced peroxidase activity and constantly high phenylalanine ammonia lyase activity in pea roots. These data suggest the involvement of these enzymes in pea resistance to crenate broomrape induced by the compatible rhizobia. Management of Orobanche via crop selection based on these enzyme systems is a viable option.     

Characterization of an Alginate Lyase,FlAlyA, from Flavobacterium sp. Strain UMI-01 and Its Expression in Escherichia coli

A major alginate lyase, FlAlyA, was purified from the periplasmic fraction of an alginate-assimilating bacterium, Flavobacterium sp. strain UMI-01. FlAlyA showed a single band of ~30 kDa on SDS-PAGE and exhibited the optimal temperature and pH at 55 °C and pH 7.7, respectively. Analyses for substrate preference and reaction products indicated that FlAlyA was an endolytic poly(mannuronate) lyase (EC 4.2.2.3). A gene fragment encoding the amino-acid sequence of 288 residues for FlAlyA was amplified by inverse PCR. The N-terminal region of 21 residues except for the initiation Met in the deduced sequence was predicted as the signal peptide and the following region of six residues was regarded as propeptide, while the C-terminal region of 260 residues was regarded as the polysaccharide-lyase-family-7-type catalytic domain. The entire coding region for FlAlyA was subjected to the pCold I—Escherichia coli BL21(DE3) expression system and ~eight times higher yield of recombinant FlAlyA (recFlAlyA) than that of native FlAlyA was achieved. The recFlAlyA recovered in the periplasmic fraction of E. coli had lost the signal peptide region along with the N-terminal 3 residues of propeptide region. This suggested that the signal peptide of FlAlyA could function in part in E. coli.     

植物保卫素东莨菪内酯对烟草的诱导抗性研究进展

东莨菪内酯属香豆素类化合物,是烟草中重要的植物保卫素,能抗烟草花叶病、灰霉病、野火版、青枯病、黑胫病等多种病害,其在烟草组织中通过苯丙氨酸解氨酶(PAL)调控合成,当受到不良环境影响或者外源物质(茉莉酸甲酯、2,4-D、核黄素、细胞分裂素等)诱导时,东莨菪内酯在烟草葡萄糖基转移酶(TOGTs)调控转化为东莨菪苷转移到液泡中发挥抗病作用。该文综述了东莨菪内酯对烟草中的生物合成及诱导抗性的相关研究,以期为提高烟草的抗病性及防治提供理论依据。     

禾谷镰刀菌武昌菌株毒素的毒性分析

为提高小麦抗赤霉病体细胞的筛选效果，对禾谷镰刀菌武昌菌株的产毒、毒素提取、纯化、毒素组分及毒素初定量进行了研究。麦粒培养基培养２５天后可检测到两个主要毒性组分（Ａ和Ｂ）。其特征吸收峰值分别为２７０和２７５ｎｍ，Ｒｆ值分别为０．４５和０．５５左右。ＳＰＭ培养基培养只能检测到组分Ａ。Ａ组分与脱氧雪腐镰刀菌烯醇（ＤＯＮ）的结构特征基本相同。经高压灭菌的毒素可渗入到培养基中作抗性愈伤组织的筛选剂。毒素对愈     

藻蓝蛋白α亚基裂合酶的分子克隆和酶动力学研究

为了比较研究不同藻种中藻蓝蛋白裂合酶CpcE/F的结构与功能的差异,对Anabaena sp.PCC 7120中的CpcE/F进行克隆,并进行大量表达,将表达的裂合酶CpcE/F用于藻蓝胆素(PCB)与Mastigocladus laminosus PCC 7603藻蓝蛋白α-亚基(α-PC)脱辅基蛋白(CpcA)的体外重组,得到天然活性的α-PC,从而表明CpcE/F所编码的蛋白质是α-PC生物合成的裂合酶,并对CpcE/F的酶动力学进行了初步研究。     

Response of in vitro obtained oil palm and interspecific OxG hybrids to inoculation with Phytophthora palmivora

Bud rot (BR) disease caused by Phytophthora palmivora is the most devastating disease in oil palm cultivation in America. Oil palms that survived BR epidemics were found in areas highly devastated by the disease; these palms were introduced into Cenipalma's in vitro micropropagation (cloning programme). A severity scale was developed for in vitro palms from five ortets inoculated with two different P. palmivora isolates. Then, eight ortets of Elaeis guineensis and two ortets of the OxG interspecific hybrid were evaluated in two inoculation trials under chamber growth conditions. The clone performance response was consistent with that reported in the field for the corresponding ortets, and two contrasting ortets, one susceptible (ortet 57) and one resistant (ortet 34) were identified. We monitored and compared defence responses to P. palmivora in the contrasting ortets. An increase in reactive oxygen species (ROS) production after inoculation with the pathogen was observed, with higher accumulation of H₂O₂ in the resistant plants. Catalase (CAT) activity in resistant plants increased after inoculation with the pathogen from 24 hr post‐infection (hpi) and remained high during the observation time. In the susceptible ortets, there was a significant increase on catalase activity only at 48 hpi. Peroxidase (POS) activity increased in clones from both susceptible and resistant ortets, but the increase was much greater in the susceptible ones. Phenylalanine ammonia lyase activity increased in response to inoculation, and these increases were greater in clones of the susceptible ortet than in clones of the resistant ortet.     

杧果炭疽病菌 3 个果胶裂解酶基因序列特征及受漆酶基因Lac1 影响的分析

果胶裂解酶是炭疽菌在侵染寄主过程中降解寄主细胞壁的一类重要水解酶。本研究在杧果炭疽病菌中克隆获得了 3 个果胶裂解酶基因 Cgpel1、Cgpel2 和 Cgpel3，DNA 全长分别为 1 037、1 498、1 089 bp，cDNA 全长分别为 975、 1 380、978 bp，分别编码 324、459、325 个氨基酸，均含 1 个果胶裂解酶保守结构域，均有典型的信号肽，不存在跨膜结构。其二级结构中 α-螺旋分别占 16.05%、20.26%、16.92%，延伸链分别占 28.09%、21.79%、29.54%，β-转角分别占 5.86%、8.93%、7.38%，无规则卷曲分别占 50.00%、49.02%、46.15%。Cgpel1、Cgpel2 和 Cgpel3 的氨基酸序列分别与 C. tofieldiae（KZL77240.1）、草莓炭疽菌（C. gloeosporioides）（XP-007274932.1）、C. incanum（KZL84476.1）果胶裂解酶序列相似度在 93%以上。qRT-PCR 分析发现，3 个果胶裂解酶基因在整个侵染过程中均持续高效表达，但在漆酶基因 Lac1 敲除突变体中，表达均下降约 90%。可见 Cgpel1、Cgpel2 和 Cgpel3 是果胶裂解酶基因家族成员，序列差异较大，在侵染过程中起着重要的作用，且其表达受漆酶基因 Lac1 影响。     

杨树溃疡病菌三菌系及诱导物对寄主两种酶活性的影响

测定了杨树溃疡病菌（Ｄｏｔｈｉｏｒｅｌａｇｒｅｇａｒｉａ）三菌系直接感染及三菌系代谢产物、菌丝体提取物等两类诱导物诱导毛白杨（Ｐｏｐｕｌｕｓｔｏｍｅｎｔｏｓａ）愈伤组织过氧化物酶和苯丙氨酸解氨酶的活性。结果表明,两个不同生理型的杨树溃疡病菌对寄主过氧化物酶活性的诱导作用差异较大,但对苯丙氨酸解氨酸活性诱导作用的大小与不同生理型之间没有必然联系