Pathogen-induced expression of cyclo-oxygenase homologue in hot pepper (Capsicum annuum cv. Pukang).

The hypersensitive reaction (HR) in plants is typified by a rapid and localized cell death at the site of pathogen infection. To understand better the molecular and cellular defence mechanism controlling HR, hot pepper leaves (Capsicum annuum cv. Pukang) were inoculated with the soybean pustule pathogen Xanthomonas campestris pv. glycine 8ra. By using the DD-PCR technique, a cDNA fragment was identified that exhibited a sequence similarity to the recently identified tobacco pathogen-induced oxygenase (PIOX) with homology to animal cyclo-oxygenase (COX). Subsequently, the full-length cDNA clone, pCa-COX1, encoding the COX homologue from the pathogen-inoculated hot pepper leaf cDNA library was isolated. The deduced amino acid sequence of Ca-COX1 shares 85.8% identity with tobacco PIOX and displays a significant degree of sequence identity (21.7-23.7%) with mammalian COXs. The expression of Ca-COX1 was markedly induced at 4-12 h after pathogen infection, while HR cell death on pepper leaves appeared at approximately 15 h post-inoculation. These results are consistent with the notion that the lipid-derived signalling pathway is involved in the initial response of hot pepper plants to pathogen infection.     

Plant regeneration in tissue cultures of pepper (Capsicum annuum L. cv. mathania)

Leaf, stem, hypocotyl, cotyledon, root, shoot tip and embryo explants of Capsicum annuum L. cv. mathania were cultured on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurine (BAP) or kinetin (Kin) alone or in combination with 3-indoleacetic acid (IAA), 3-indolebutyric acid (IBA), α-naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). BAP (5.0 mgl⁻¹) in the medium was found to be the best growth regulator for shoot bud differentiation. Shoot buds cultured on 5.0 mgl⁻¹ BAP increased in number but did not elongate. For obtaining complete plantlets, shoot buds were placed on a medium with IBA or NAA (0.1 mgl⁻¹). Histological evidence revealed direct differentiation of buds from cotyledons. Regenerated plants were normal diploids. Unorganized callus could not be induced to differentiate shoot buds.     

Satellite-RNA-mediated resistance to cucumber mosaic virus in transgenic plants of hot pepper (Capsicum annuum cv. Golden Tower)

We previously established a system of in vitro regeneration and Agrobacterium-mediated transformation for hot pepper plants. The level of protection against cucumber mosaic virus in the progeny of the transgenic hot pepper plants that express cucumber mosaic virus (CMV) satellite RNA was investigated. The transgenic hot pepper plants were self-fertilized, and their progeny were tested for stable inheritance and expression of the cDNA of CMV satellite RNA. Polymerase chain reaction and RNA gel blot analyses showed that the introduced gene was stably transmitted and expressed in the progeny. Symptom attenuation in the offspring was confirmed upon inoculation with CMV-Y or CMV-Korea (CMV-Kor) strains. Received: 30 September 1996 / Revision received: 5 May 1997 / Accepted: 22 May 1997     

Light-dark regulation of carotenoid biosynthesis in pepper (Capsicum annuum) leaves

The carotenoid content in photosynthetic plant tissue reflects a steady state value resulting from permanent biosynthesis and concurrent photo-oxidation. The contributions of both reactions were determined in illuminated pepper leaves. The amount of carotenoids provided by biosynthesis were quantified by the accumulation of the colourless carotenoid phytoene in the presence of the inhibitor norflurazon. When applied, substantial amounts of this rather photo-stable intermediate were formed in the light. However, carotenoid biosynthesis was completely stalled in darkness. This switch off in the absence of light is related to the presence of very low messenger levels of the phytoene synthase gene, psy and the phytoene desaturase gene, pds. Other carotenogenic genes, such as zds, ptox and Icy-b also were shown to be down-regulated to some extent. By comparison of the carotenoid concentration before and after transfer of plants to increasing light intensities and accounting for the contribution of biosynthesis, the rate of photo-oxidation was estimated for pepper leaves. It could be demonstrated that light-independent degradation or conversion of carotenoids e.g. to abscisic acid is a minor process.     

Increased photoinhibition in dehydrated leaves of hot pepper (Capsicum annuum L.) is not accompanied by an incremental loss of functional PSII

We examined the photosynthetic responses to photoinhibition in dehydrated leaves of hot pepper (Capsicum annuum L.). Stress was induced by immersing the roots of whole plants in Hoaglands solution containing polyethylene glycol (PEG) under high light (900 μmol photons m^-2 · s^-1). This PEG-treatment lowered the leaf water potential and the maximal rate of photosynthetic O₂ evolution (Pmax) linearly, in a time-dependent manner, to about 50% inhibition after 6 h. Pmax also decreased linearly as the period of high-light treatment lengthened. That inhibitory response was not as extreme, showing about 30% inhibition after 6 h. However, when the treatments of dehydration and high light were simultaneously administered, Pmax decreased more rapidly, in a synergistic fashion, showing about 90% inhibition within 2 h. Dehydration, in contrast to the light treatment, did not lower the maximal photochemical efficiency (Fv/Fm). Furthermore, this decline in Fv/Fm for light-treated, dehydrated leaves was almost identical to the response of photoinhibited leaves that were not dehydrated. Similar changes were observed in the number of functional PSII complexes. The decrease in Pmax and the amount of functional PSII was linearly correlated in photoinhibited leaves, but not in dehydrated leaves, regardless of light treatment. Therefore, we have demonstrated that exacerbated photoinhibition in dehydrated leaves occurs without an incremental loss of functional PSII.     

Constitutive expression of rice MADS box gene using seed explants in hot pepper (Capsicum annuum L.).

Two transgenic pepper plants were obtained from 255 seed explants that were infected with Agrobacterium LBA4404 (pGA1209). One of them (PT2) showed morphological change, such as dwarfism and early flowering by the constitutive expression of the rice OsMADS1 gene. The in vitro condition of the plant regeneration has been optimized from hypocotyl explants on a MS medium that was supplemented with zeatin 3 mg/L, IAA 0.3 mg/L for shoot induction. The optimal rooting condition was at NAA 0.3 mg/L. The transformation frequency was 0.8% from the total hypocotyls. DNA and RNA hybridization analyses showed that the introduced gene was integrated and stably expressed in regenerated plants.     

辣椒31个优良自交系的亲本类群分析

以包含我国重要尖椒品种的亲本材料在内的31份优良自交系为材料, 利用SRAP标记和基因型值分析技术开展了辣椒自交系间遗传差异的分析与类群划分研究。结果表明: 在30个引物组合中, 27个引物组合可以 在自交系间扩增出多态性条带, 共扩增出310个多态性条带, 平均每个引物组合产生11.5个多态性条带, 显示出SRAP技术具有较强的分析效率; 基于SRAP标记和Yule相似系数对这些自交系进行的聚类分析中, 可以基本区分辣椒的2个变种(C. annuum var. grossum和C. annuum var. longum), 而且可以反映出自交系间的亲缘及系谱关系; 在相似系数为0.67处, 可将这31个自交系分为4个类群; 基于基因型值和标准Euclidean距离对这些自交系进行的聚类分析可成功地将辣椒的两个变种完全区分; 在遗传距离约4.5处, 可将这31个自交系分为4个类群; 自交系间基于SRAP标记与基因型值的遗传距离存在一定的相关性。     

Capsinoid is biosynthesized from phenylalanine and valine in a non-pungent pepper, Capsicum annuum L. cv. CH-19 sweet

The biosynthetic pathway of capsinoid in 'CH-19 Sweet' was investigated. [(3)H]Valine and [(14)C]phenylalanine were injected into the fruits of the intact plant. Both of radioactivities were detected in capsinoid fractions. (14)C radioactivity was observed in phenylpropanoid compounds, and in vanillin, vanillylamine, vanillyl alcohol, and vanillic acid. We confirmed that capsinoid is biosynthesized from phenylalanine and valine.     

In vitro morphogenetic responses and plant regeneration from pepper (Capsicum annuum L. cv. Early California Wonder) seedling explants

Explants from 13-d old pepper (Capsicum annuum, L. cv. Early California Wonder) seedlings were cultured in Murashige and Skoog (MS) medium supplemented with different levels of 1-naphthalene acetic acid (NAA) and 6-benzylamino purine (BAP). Multiple shoot-buds proliferated from the cut surfaces of cotyledon, shoot-tip and hypocotyl explants in one month. The best NAA to BAP combinations (mg/l: mg/l) for multiple shoot-bud regeneration of the above three explant types were 0.1 ∶ 5.0, 0.0 ∶ 5.0, and 0.1 ∶ 10.0, respectively. Root explants did not express any new morphogenetic response in all hormonal combinations tested. Regenerated shoot-buds were excised from the explants and cultured in 1/2X or 1X MS medium supplemented with different levels of Indole-3-acetic acid (IAA) or NAA. When cultured in full strength MS medium with 0.5 mg/l IAA or 0.4 mg/l NAA, 70% of the buds rooted in one month. Plantlets were established successfully ex vitro under greenhouse mist and grown to maturity.     

Isolation and characterization of acid invertase cDNA clone in hot pepper (Capsicum annuum L.) fruits

An acid invertase (EC 3.2.1.26.) cDNA clone,CaAIV-18, was isolated from the red pericarp cDNA library of the hot pepper (Capsicum annuum L.) fruit. TheCaAIV-18 clone has 2223 nucleotides and one open reading frame encoding 641 amino acid residues. Analysis of deduced amino acid sequences reveals thatCaAIV-18 has a 24-amino acid transmembrane anchor region in its N-terminal, implying acid invertase in hot pepper may be localized in the membrane and not in the cytosol. This clone showed high homology to tomato acid invertase,Aiv1, in nucleotide and deduced amino acid sequences. In the Southern blot analysis, this clone proved to exist as single or low copy numbers on the genome of hot pepper. The clones had two well-conserved regions which appears in acid invertase of other plant species (eg. tomato,Arabidopsis, etc.) and yeasts. During fruit development,CaAIV-18 was expressed preferentially in the ripe red stage.