Role of Jasmonic Acid as a Signaling Molecule in Copper Chloride-elicited Rice Phytoalexin Production

Phytoalexins are antimicrobial secondary metabolites which accumulate in plants against fungal invasion. Their production is triggered not only by fungal invasion, but also by a variety of elicitors. In rice plants, we have shown that CuCl₂ is a potent abiotic elicitor. Jasmonic acid has recently become known to play an important role in secondary metabolite production in plants at the cellular level. This led us to speculate, in CuCl₂-elicited rice leaves, that JA might also play an important role as a signal transducer for phytoalexin production. The endogenous level of JA increased rapidly in CuCl₂-elicited rice leaves, and exogenously applied JA caused a large amount of phytoalexin production in rice leaves. This phytoalexin production by CuCl₂ decreased when rice leaves were treated with JA biosynthesis inhibitors, but that by JA did not. JA is thus suggested to play an important role in the elicitation process leading to phytoalexin production in rice leaves.     

Facile preparation of optically active jasmonates and their biological activities in rice

A facile and efficient method has been developed for the optical resolution of racemic jasmonic acid (JA) on a relatively large scale and was successfully utilized for the preparation of optically pure (+)-JA and (?)-JA. We indicated that (+)-JA has lower growth inhibitory activity than (?)-JA in the rice seedling growth test and confirmed in line with an earlier observation that their respective biologically-active forms, (+)-JA-Ile and (?)-JA-Ile, show comparable inhibitory activities. We compared the metabolism of (+)-JA and (?)-JA into (+)-JA-Ile and (?)-JA-Ile, respectively, in the JA-deficient rice cpm2, and found that the exogenously applied (+)-JA was metabolized to the corresponding Ile conjugate less efficiently as compared with (?)-JA. Such metabolic rate difference may cause a discrepancy between biological potencies of (+)-JA and (?)-JA in rice.

Abbreviations: FW: fresh weight; Ile: isoleucine; JA: jasmonic acid; JA-Ile: jasmonoyl-l-isoleucine; LC-ESI-MS/MS: liquid chromatography and electrospray ionization tandem mass spectrometry; MeJA: methyl jasmonate; OPDA: 12-oxophytodienoic acid     

Potato cysteine proteinase inhibitor gene family: molecular cloning,characterisation and immunocytochemical localisation studies

Potato cysteine proteinase inhibitors (PCPIs) represent a distinct group of proteins as they show no homology to any other known cysteine proteinase inhibitor superfamilies, but they all belong to the Kunitz-type soybean trypsin inhibitor family. cDNA clones for five PCPIs have been isolated and sequenced. Amino acid substitutions occurring in the limited regions forming loops on the surface of these proteins suggest a further classification of PCPIs into three subgroups. Accumulation of PCPI was observed in vacuoles of stems after treatment with jasmonic acid (JA) using immunocytochemical localisation, implying that these inhibitors are part of a potato defence mechanism against insects and pathogens. Genomic DNA analysis show that PCPIs form a multigene family and suggest that their genes do not possess any introns.     

Sulfoquinovosyldiglyceride and Triglycosyldiglyceride in Rice Grains

Sulfoquinovosyldiglyceride and triglycosyldiglyceride were isolated from rice grains, mainly by column chromatography and thin-layer chromatography. The major component fatty acids were palmitic, oleic, stearic and linoleic acids in sulfoquinovosyldiglyceride whereas they were linoleic, palmitic and oleic acids in triglycosyldiglyceride, in decreasing order of amount. The component sugar in sulfoquinovosyldiglyceride was sulfoquinovose, while those in triglycosyldiglyceride were galactose and glucose, the latter being predominant.     

甲醇介导昆虫与植物的防卫反应

综述甲醇介导的昆虫与植物的互作关系。害虫为害使寄主植物释放大量甲醇。这是由于害虫唾液的碱性性质提高了果胶甲基酯酶的活性,上调了果胶甲基酯酶基因的转录,水解果胶而即时释放出大量甲醇。果胶甲基酯酶则可能通过改变细胞壁结构特性而间接激发茉莉酸和水杨酸信号途径,从而启动植物防卫物质如胰蛋白酶抑制剂的合成。此外,甲醇还可能作为信号物质,影响害虫定向。外施甲醇于健康植物则可能通过负反馈机制抑制植物防卫反应,从而影响植食者。     

Pib启动子中茉莉酸和乙烯响应元件的转基因分析

水稻Pib基因的表达受茉莉酸、乙烯等激素诱导, 为了确定该基因启动子响应茉莉酸和乙烯诱导的必需区域, 进一步阐明茉莉酸和乙烯响应分子元件, 文章用PCR制备了Pib全长启动子-3 572~2 bp及3个5′端有不同长度缺失的Pib启动子片段-2 692~2 bp、-1 335~2 bp、-761~2 bp。4个不同长度Pib启动子分别置换掉双元质粒中gus基因上游的35S构建为重组质粒, 经农杆菌介导转入水稻获得转基因植株。转基因水稻中gus活性的蛋白质水平和mRNA水平的定性和定量分析结果表明, 全长Pib启动子(-3 572~2 bp, pNAR901)启动活性最强, 茉莉酸或乙烯诱导6 h后, 其驱动gus基因在转基因植株各部组织中的表达量明显上升。而-3 572~-2 692 bp区段序列缺失后不但Pib启动子启动活性显著降低而且也丧失了对茉莉酸和乙烯的诱导活性。pNAR902(-2 692~2 bp),pNAR903(-1 335~2 bp)和pNAR904(-761~2 bp)中的Pib启动子序列的缺失长度相差达2倍和3倍以上, 但其对茉莉酸和乙烯的诱导响应没有区别。这些结果显示3个Pib启动子缺失体构建中, 其共同缺失序列即-3 572~-2 692 bp区域是Pib启动子茉莉酸和乙烯诱导响应的必需区域。软件检索证实, Pib启动子序列中只在上述共同缺失区段之内的-2 722 bp处有一个GCCGCC基序。文章报道的转基因实验表明GCCGCC基序可能是Pib基因中有关茉莉酸和乙烯诱导响应的顺式分子元件。     

Triacontanol negatively modulates the jasmonic acid-stimulated proteinase inhibitors in tomato (Lycopersicon esculentum)

Triacontanol (TRIA), a long chain aliphatic alcohol (C30H61OH) reverses the effect of jasmonic acid (JA) in inducing proteinase inhibitors (PIs) in tomato leaves. Porcine pancreas trypsin and Spodoptera litura gut proteinases were inhibited in the presence of leaf proteins treated with JA, and TRIA partially reverses this effect. Spodoptera litura larvae fed with tomato leaves treated with JA were reduced in body weight and TRIA is able to partially reverse this JA-induced effect. These results reflect the partial reversal effect of TRIA in down regulating the JA-induced production of proteinase inhibitors.     

The Occurrence of Renin Inhibitor in Rice: Isolation,Identification, and Structure-Function Relationship

We found renin inhibitory activity in rice. The physico-chemical data on the isolated inhibitors were identical to those of oleic acid and linoleic acid. Oleic acid and linoleic acid competitively inhibited renin activity, with K_i values of 15.8 and 19.8 μM respectively. Other unsaturated free fatty acids also inhibited renin activity, but saturated fatty acids had no effect on it.