Chlorophyll-deficient Mutations Research Articles

The potential effects of chlorophyll-deficient mutation and tree_age on the accumulation of amino acid components in tea plants

Albino tea has been receiving growing attention on the tea market due to its attractive appearance and fresh taste, mainly caused by high amino acid contents. Here, variations in the contents of five free amino acids in relation to pigment contents and tree age in two hybrid populations‘Longjin 43′(♀) × ‘Baijiguan’(♂) and ‘Longjin 43′(♀) בHuangjinya’(♂) with 334 first filial generation individuals including chlorophyll-deficient and normal tea plants were investigated. The data showed that the contents of main amino acids in all filial generation gradually decreased as plant age increased. Principal component analysis indicated that the amino acid content of individual plant tended to be stable with the growth of plants. Correlation analysis clarified that several main amino acids were significantly negatively correlated with chlorophyll a, chlorophyll b and carotenoid contents. Our results showed that the accumulation of amino acids in tea plant was closely related to leaf color variation and the tree age during growing period.

The chlorophyll-deficient golden leaf mutation in cucumber is due to a single nucleotide substitution in CsChlI for magnesium chelatase I subunit.

The cucumber chlorophyll-deficient golden leaf mutation is due to a single nucleotide substitution in the CsChlI gene for magnesium chelatase I subunit which plays important roles in the chlorophyll biosynthesis pathway. The Mg-chelatase catalyzes the insertion of Mg(2+) into the protoporphyrin IX in the chlorophyll biosynthesis pathway, which is a protein complex encompassing three subunits CHLI, CHLD, and CHLH. Chlorophyll-deficient mutations in genes encoding the three subunits have played important roles in understanding the structure, function and regulation of this important enzyme. In an EMS mutagenesis population, we identified a chlorophyll-deficient mutant C528 with golden leaf color throughout its development which was viable and able to set fruits and seeds. Segregation analysis in multiple populations indicated that this leaf color mutation was recessively inherited and the green color showed complete dominance over golden color. Map-based cloning identified CsChlI as the candidate gene for this mutation which encoded the CHLI subunit of cucumber Mg-chelatase. The 1757-bp CsChlI gene had three exons and a single nucleotide change (G to A) in its third exon resulted in an amino acid substitution (G269R) and the golden leaf color in C528. This mutation occurred in the highly conserved nucleotide-binding domain of the CHLI protein in which chlorophyll-deficient mutations have been frequently identified. The mutant phenotype, CsChlI expression pattern and the mutated residue in the CHLI protein suggested the mutant allele in C528 is unique among mutations identified so far in different species. This golden leaf mutant not only has its potential in cucumber breeding, but also provides a useful tool in understanding the CHLI function and its regulation in the chlorophyll biosynthesis pathway as well as chloroplast development.

Characterization and mapping of novel chlorophyll deficient mutant genes in durum wheat

The yellow-green leaf mutant has a non-lethal chlorophyll-deficient mutation that can be exploited in photosynthesis and plant development research. A novel yellow-green mutant derived from Triticum durum var. Cappelli displays a yellow-green leaf color from the seedling stage to the mature stage. Examination of the mutant chloroplasts with transmission electron microscopy revealed that the shape of chloroplast changed, grana stacks in the stroma were highly variable in size and disorganized. The pigment content, including chlorophyll a, chlorophyll b, total chlorophyll and carotene, was decreased in the mutant. In contrast, the chla/chlb ratio of the mutants was increased in comparison with the normal green leaves. We also found a reduction in the photosynthetic rate, fluorescence kinetic parameters and yield-related agronomic traits of the mutant. A genetic analysis revealed that two nuclear recessive genes controlled the expression of this trait. The genes were designated ygld1 and ygld2. Two molecular markers co-segregated with these genes. ygld 1 co-segregated with the SSR marker wmc110 on chromosome 5AL and ygld 2 co-segregated with the SSR marker wmc28 on chromosome 5BL. These results will contribute to the gene cloning and the understanding of the mechanisms underlying chlorophyll metabolism and chloroplast development in wheat.

Fine mapping of a Xantha mutation in rice (Oryza sativa L.)

The recessive mutation of the XANTHA gene (XNT) transforms seedlings and plants into a yellow color, visually distinguishable from normal (green) rice. Thus, it has been introduced into male sterile lines as a distinct marker for rapidly testing and efficiently increasing varietal purity in seed and paddy production of hybrid rice. To identify closely linked markers and eventually isolate the XNT gene, two mapping populations were developed by crossing the xantha mutant line Huangyu B (indica) with two wild type japonica varieties; a total of 1,720 mutant type F2 individuals were analyzed for fine mapping using polymorphic InDel markers and high dense microsatellite markers. The XNT gene was mapped on chromosome 11, within in a fragment of ~100 kb, where 13 genes are annotated. The NP_001067671.1 gene within the delimited region is likely to be a candidate XNT gene, since it encodes ATP-dependent chloroplast protease ATP-binding subunit clp A. However, no sequence differences were observed between the mutant and its parent. Bioinformatics analysis demonstrated that four chlorophyll deficient mutations that were previously mapped on the same chromosome are located outside the XNT region, indicating XNT is a new gene. The results provide useful DNA markers not only for marker assisted selection of the xantha trait but also its eventual cloning.

Allelism and molecular mapping of soybean necrotic root mutants

Mutability of the w4 flower color locus in soybean, Glycine max (L.) Merr., is conditioned by an allele designated w4-m. Germinal revertants recovered among self-pollinated progeny of mutable plants have been associated with the generation of necrotic root mutations, chlorophyll-deficiency mutations, and sterility mutations. A total of 24 necrotic root mutant lines were generated from a total of 24 independent reversion events at the w4-m locus. The initial mutable population included 4 mutable categories for w4-m, designated (1) low frequency of early excisions, (2) low frequency of late excisions, (3) high frequency of early excisions, and (4) high frequency of late excisions. These mutable categories were based upon flower phenotype, i.e., somatic tissue. A total of 22 of 24 necrotic root mutations occurred from germinal reversions classified in the high frequency of excision categories. Of these 22 mutants, 14 came from early excisions and 8 came from late excisions. These necrotic root mutants were allelic to 6 previously identified necrotic root mutants derived from the study of germinal revertants, i.e., gene tagging studies, chemical mutagenesis, and "spontaneous" occurrences from genetic crosses. Thus, all 30 necrotic root mutants in soybean are allelic. An F2 mapping population from the cross of Minsoy (Rn1 Rn1) x T328 (rn1 rn1) was used to map the Rn1 locus using simple sequence repeat (SSR) markers. The Rn1 locus was located between Satt288 and Satt612 on molecular linkage group G.

Influence of potassium cyanide on the azide mutagenesis in barley.

The activity of potassium cyanide (KCN) alone or in combination with sodium azide (SA) on barley mutagenesis was studied in five different experiments. It was measured by frequencies of chlorophyll-deficient mutations per M1 spikes. The M1 plant sterility and lethality were also studied. In single treatments KCN showed no mutagenic activity, as well as a low level of injury in M1 plant sterility and lethality. On the other hand, SA treatments alone were highly effective for inducing both chlorophyll mutations and sterility, but at a low level of lethality. KCN in post- and simultaneous treatments combined with SA treatment has produced a marked reduction of the frequencies of SA-induced chlorophyll-deficient mutations and sterility. The decrease was much less when KCN was pretreatment. None of the combined treatments produced high levels of M1 plant lethality.

Influence of mature and immature sunflower seed treatment with ethylmethanesulphonate on mutation spectrum and frequency

SUMMARY The frequency and spectrum of morphological mutations, raised in M2 after sunflower mature and immature seed treatment with ethylmethanesulphonate (EMS), were studied. Mature seeds of 3 self-pollinated lines (ZL9, ZL102, ZL169) and immature seeds of 2 lines (ZL102 and ZL169) were treated with EMS at the concentrations of 0.01%, 0.1% and 0.5% for 6 and 12 h and 0.01% and 0.1% for 6 and 12 h, respectively. We isolated and described 18 types of mutation, which were classified into the following groups: chlorophyll deficiency (6), leaf (5), stem and (4) ray floret shape and color (3). Genotypic differences were revealed for the spectrum of mutations occurring after mutagenic treatment of mature and immature seeds. Differences in mutation spectrum existed in the studied lines after treatment of mature seeds. Mutation frequency after immature seed treatment did not exceed the amount of mutations after mature seed treatment where the maximum frequency amounted to 13.2%. Chlorophyll deficiency mutations averaged a half and more of the visible morphological mutations. RESUMEN La frecuencia y el spectro de mutaciones morfologicas separadas en M2 despues del tratamiento de las semillas maduras y no maduras de girasol con etilometanosulfonato (EMS) fueron estidiados. Semillas maduras de tres lineas Zl9, Zl102, Zl169 y semillas no maduras de dos lineas Zl102, Zl169 fueran tratadas con EMS en las concentraciones de 0.01%, 0.1%, 0.5% durante 6 y 12 horas y 0.01%, 0.1% durante 6 y 12 horas, respectivamente. Fueron obtenidos y descritos 18 tipos de mutaciones que fueron combinados en los grupos siguientes: insuficiencia clorofilica (6), mutaciones de hoja (5), mutaciones de tallo (4), mutaciones de forma y color de flores de rayo (3). Diferencias genotipicas fueran reveladas para el spectro de mutaciones mostrado despues del tratamiento mutagenico de las semillas maduras y no maduras asi como las diferencias para el spectro mutacionico de las lineas estudiadas despues del tratamiento de las semillas maduras. La frecuencia mutacionica despues del tratamiento de las semillas no maduras no superada la cantidad de mutaciones despues del tratamiento de las semillas maduras donde la frecuencia maximala fue 13.2%. Las mutaciones de insuficiencia clorofilica han formado la mintad y mas de mutaciones morfologicas visibles. RÉSUMÉ La fréquence et le spectre des mutations morphologiques dans la génération M2 après le traitement de la semence mature et immature à l’éthyle méthane sulphonate (EMS) ont été analysés. Les semences matures de trois lignées autofécondées (ZL9, ZL 102, ZL169) ont été traitées au EMS en concentrations de 0,01%, 0,1%, 0,5% aux 6 et 12 heures et les semences immatures des deux lignées (ZL102 et ZL169) en concentrations de 0,01%, 0,1% aussi aux 6 et 12 heures. Nous avons isolé et décrit 18 types de mutations qui ont été placées dans les groupes suivants : manque de chlorophylle (6), feuille (5), tige (4) et forme et couleur des fleurons ligulés (3). Après le traitement mutagène des semences matures et immatures, des différences génotypiques sont apparues dans le spectre de la mutation. Dans le cas des semences immatures, la fréquence de mutation n’a pas dépassé le nombre de mutations de la semence mature où la fréquence maximale était de 13,1%. Les mutations de type déficience en chlorophylle comptaient pour la moitié et plus des mutations morphologiques visibles.

Chlorophyll-deficient propagules of Avicennia marina and apparent longer term deterioration of mangrove fitness in oil-polluted sediments

A correlation between petroleum hydrocarbon concentrations in sediments and chlorophyll-deficient mutations in mangroves may occur also in Australian mangroves. Earlier reports of such mutations in the Caribbean area were evident in viviparous propagules of the common mangrove genera, Rhizophora, borne on otherwise normal trees. These mutant propagules were termed ‘albinos’ since they lacked chlorophyll and normal green coloration, leaving them white, yellow or red. The mutation was considered lethal since newly established albino seedlings appeared unable to survive more than a few months. Our preliminary investigation of mangroves in SE Queensland found a similar mutation in another common mangrove genus, Avicennia, and this was apparently also correlated with oil concentrations in sediments. Although, more evidence is required, an apparently similar relationship shows that whatever caused the mutations may act commonly across a diverse range of plant types in quite separate locations. How widespread might this mutation be in mangroves? How many genera and species are affected? Are all occurrences correlated with oil in sediments? Does oil cause the mutation? We discuss these important questions and the potentially serious implications to coastal management where high mutant densities may be indicative of longer term genetic deterioration of mangrove habitat in oil-polluted wetland environments.

Chlorophyll-deficient gene and morphological variations in Korean populations of maize (Zea mays)

We studied cultivated and naturalized Korean maize populations to determine the extent to which the chlorophylldeficient mutation and the phenotypic variations of two morphological characters (i.e., red coleoptiles and epicotyls, and the number of the first root hairs) are maintained. The frequency of the chlorophyll-deficient mutant gene (2.73% on average) was highly variable. Frequencies of red coleoptiles and epicotyls also were higher than expected from a mutation-selection balance. The average number of hairy phenotypes within populations was 1.8, ranging from 0.0 to 4.0. Naturalized populations were closely related to with cultivated communities. Most striking, however, was the more significant difference among populations than within populations with regard to both the frequency of chlorophyll-deficient mutant genes and the phenotypic variations of our two morphological characters. On a per-gene basis, the majority of the phenotypic variation (mean of 73.3%) resided among populations.

Mutagenesis and in vitro culture of Tillandsia fasciculata Swartz var. fasciculata (Bromeliaceae)

The genus Tillandsia (Bromeliaceae) has very few variegated species, and cultivars with chlorophyll-deficient variegation are especially rare. With the objective of inducing chlorophyll-deficient leaf variegation, seeds of Tillandsia fasciculata var. fasciculata were treated with gamma radiation, combined gamma and thermal neutron radiation or by chemical mutagenesis with ethyl methanesulfonate (EMS). Wild type, albino, yellow, yellowish-green and variegated phenotypes were obtained in the subsequent M 0 generation. These variegated seedlings were either sectorial or mericlinal chimeras, consequently the variegation of these seedlings was lost as they grew older. Gamma radiation at 21 kR and 27 kR produced the highest percentage of variegated seedlings (4.4%). The highest percentage of seedlings with chlorophyll-deficient leaves was 8.4% with 27 kR gamma radiation, and 15.8% with 1.2% EMS. Radiation and chemical mutagenesis caused chlorophyll-deficiency mutations in one or more of the histogenic layers: LI, LII, LIII. Wild types had greater total chlorophyll a, b and total chlorophyll than mutant phenotypes. Most of the yellow and yellowish-green seedlings multiplied in a solid half-strength MS medium with equimolar 0.3 or 0.5 μM BA and IBA. The yellowish-green seedlings were able to grow photoautotrophically while the yellow ones were not. This is one of the first reports on the mutagenesis of a Tillandsia species. Stable periclinal chlorophyll-deficient chimeras of Tillandsia species can likely be obtained via mutagenesis if large numbers of seeds are treated with a suitable mutagen.

Yellow-Tip: A Cytoplasmically Inherited Trait in Melon (Cucumis melo L.)

A new chlorophyll-deficient mutant is the first cytoplasmically inherited trait described in melon. This mutant is characterized by yellow apices, with the leaves and stems progressively turning green in color as the branches mature. A protocol is proposed for naming and symbolizing cytoplasmic traits in melon. This mutation is named yellow-tip and is symbolized cyt-Yt. As a chlorophyll-deficient mutation, it is potentially useful in genetic, physiological, and biochemical studies.

The effects of embryo competition with mixed mating on the genetic load in plants

Many plant species abort a large number of seeds, often producing an increase in the fitness of progeny, and a decrease in the proportion of inbred offspring. Where genetic load is caused by deleterious recessive mutations in mutation-selection balance, the removal of inbred offspring may prevent the expression of mutations as homozygotes. This would shelter the mutations from selection, and permit an increase in the genetic load relative to the case with no competition among embryos. This study employs existing models of genetic load to assess the effects of embryo competition on load. Mutations which are not expressed in the embryo (e.g. chlorophyll deficiency mutations) are sheltered from selection by the removal of inbred seed, and increase in frequency relative to the case without embryo competition. Moreover, if embryo competition is discontinued after several generations, expression of the accumulated load causes a temporary, but pronounced drop in mean fitness. By contrast, mutations which are expressed in the embryo may affect the outcome of competition, and thus experience added selection relative to the case with no competition. Genetic load at these loci may thus be reduced, although the exact outcome depends upon the expression of the mutations in heterozygotes. The mechanism of embryo competition must be known before the long-term effects of management practices which enhance embryo competition can be predicted. Even where selective abortion increases the fitness of stocks over the long term, the accumulation of additional mutations can produce a dramatic loss of fitness if selective seed abortion is discontinued. Thus, once a programme to enhance selective abortion is begun, it may be impossible to cease this programme without irreparable damage to the stocks.

Gamma-ray mutagenesis on grapevine rootstocks cultivated <em>in vitro</em> (1)

<p style="text-align: justify;">The efficiency of γ-irradiation as a tool for breeding grapevine rootstocks was investigated. One-bud cuttings from vitroplants of two varieties (Fercal and Gravesac) were subjected to gamma rays from Cs<sup>137</sup> source at rates from 10 to 60 Grays (Gy) at intervals of 10. All the parameters observed were affected at 20 Gy and upwards. Varietal susceptibility to irradiation was different since the maximum withstanding dose was 40 Gy for Gravesac and only 30 for Fercal. Besides, shoot development was more lowered than root development. The results showed that an increase of the irradiation dose decreased the rate of survival, the rhizogenesis and the growth of<em> in vitro</em> plants. On the V<sub>2</sub> vegetative generation ofGravesac vitroplants changes in size, in leafform, in plant habits, in growth and chlorophyll deficient mutations were recorded. Moreover, after a 30 Gy irradiation variations of growth, dry weight, leaf area, number of stomata and photosynthesis rates were shown on the V<sub>3</sub> generation. Accordingly this irradiation method is efficient to develop an <em>in vitro</em> variability. A sample of the surviving plants was established in the greenhouse for further screening.</p><p style="text-align: justify;"><br />(1) Communication faite au 6'®me Symposium International sur l'Amélioration de la Vigne, à Yalta (Crimée), Ukraine, du 4 au 10 septembre 1994</p>

Mangrove Genetics. II. Outcrossing and Lower Spontaneous Mutation Rates in Puerto Rican Rhizophora

The frequency of red mangrove trees, Rhizophora mangle L., that were monohybrid heterozygotes for chlorophyll-deficient alleles was determined for populations along the southwest coast of Puerto Rico. Segregation ratios for the offspring of these trees were also calculated. Although nuclear, the different mutant homozygous genotypes had profound effects on chloroplast ultrastructure. In comparison to Florida and San Salvador Island R. mangle populations, Puerto Rican mangroves were more outcrossed (28.8% vs. 4.8%) and had lower per generation per genome mutation rates for chlorophyll-deficient mutations (2.1 x 10-3 vs. 5.8 x 10-3).

Petroleum pollution and mutation in mangroves

Chlorophyll-deficiency has often been used as a sensitive genetic end-point in plant mutation research. The frequency of trees heterozygous for nuclear chlorophyll-deficient mutations was determined for mangrove populations growing along the southwest coast of Puerto Rico. The frequency of heterozygotes was strongly correlated with the concentration of polycyclic aromatic hydrocarbons in the underlying sediment and with both acute and chronic petroleum pollution. Although epidemiological studies can seldom prove causation, a strong correlation is certainly compatible with a cause-effect relationship. Our results suggest that the biota of oil-polluted habitats may be experiencing increased mutation.

EMS-induced streptomycin resistance in Solanum melongena

Streptomycin-resistant mutations were induced in Solanum melongena by exposing seeds to ethyl methane sulphonate (EMS). Seed mutagenesis resulted in a high frequency of chlorophyll-deficient mutations and a low frequency of resistant shoots, both of which retained their resistance on subsequent testing. Reciprocal crosses between streptomycin-resistant and -sensitive plants showed a non-Mendelian transmission of the resistance trait. Streptomycin resistance is the first selectable and maternally inherited organelle marker described in brinjal.

Mangrove Genetics. I. Mating System and Mutation Rates of Rhizophora Mangle in Florida and San Salvador Island, Bahamas

Mutation rates for chlorophyll deficiency in Florida and San Salvador Island red mangroves, Rhizophora mangle, are essentially identical; the average rate is 0.0058 ± 0.0018 chlorophyll-deficiency mutations per genome per generation. Segregation ratios for marker genes in the progeny of heterozygous trees support the hypothesis that selfing is very common in the populations studied. If inbreeding turns out to be prevalent throughout the range of red mangrove, mangrove forests may be essentially single-species natural monocultures with little geneticdiversity.

Chlorophyll-deficient Mutations Induced in Rice by Alkylating Agents and Azide.

The three cultivars of rice were treated with sodium azide and two alkylating agents EMS and MMS with a view to find out the frequency, spectrum, efficiency and effectiveness of chlorophyll mutations in relation to the genotype and the nature of the mutagen. Chlorophyll mutation frequency was enhanced with increasing dose but dropped at very high doses. Among the chlorophyll mutants induced viridis type formed the majority class. Effectiveness decreased with increase in dose with a few exceptions. Efficiency was more in the alkylating agents treated populations.

Monitoring and assessment of mercury pollution in the vicinity of a chloralkali plant. II Plant-availability, tissue-concentration and genotoxicity of mercury from agricultural soil contaminated with solid waste assessed in barley ( Hordeum vulgare L.)

Barley ( Hordeum vulgare L.) was used to assess plant-availability, tissue-concentration and genotoxicity of mercury from the solid waste deposits of a chloralkali plant. Seeds of H. vulgare, presoaked in distilled water, were allowed to germinate and grow on agricultural soil mixed with solid waste containing 2550 ± 339 mg Hg kg −1 at different proportions (0·75, 1·5, 2·5 and 5%). Plants raised from germinating seeds on uncontaminated agricultural soil served as controls. On day 7, germination counts and seedling heights were recorded. The concentration of mercury in soil, and plant tissue (dry weight) were determined at different stages of plant growth from day 7 till maturity and harvest. The availability of mercury from the soil was assessed by extracting mercury at a range of pH values (2–6) and by chemical methods. The embryonic shoots excised at 36 h of germination were subjected to cytological analysis to determine mitotic index and frequency of mitoses with chromosomal aberrations. The pollen mother cells from anthers of young M 1-spikes were analysed to score meiotic aberrations. Subsequently, the pollen fertility and seed set were determined. Furthermore, M 2-seedlings were analysed for chlorophyll-deficient mutations. The cytogenetic analysis revealed the effects of mercury on the mitotic and meiotic chromosomes which were significantly correlated with soil-mercury. The bioconcentration of mercury in aerial tissues decreased with the age of the plant. Roots, in particular, were found to concentrate most of the mercury taken up by the plant. At the time of harvest, the bioconcentration of mercury in straw was at a minimum. The accumulation of mercury in grain, which was significant, did not increase with the increase in concentration of mercury in soil but maintained a plateau, indicating a restriction of transport of mercury through the phloem. The unique advantage with the use of Hordeum assay is that, besides assessing the germline toxicity, the assay takes into account the possible contamination of the agricultural food-chain.

Phenotypic expression of a chlorophyll mutant in cowpea ( Vigna unguiculata): Environmental influences and effects on productivity

Phenotypic expression of a chlorophyll-deficient mutation in cowpea was studied to determine the value of this trait for plant breeding. The mutant and its parent were grown under two irradiances in growth chambers, and under two contrasting temperature regimes in glasshouses. In addition, grain-yield and biomass productivity of the mutant and parent were compared under field conditions. Under optimal temperatures, the leaves of the mutant exhibited significantly lower chlorophyll content per unit leaf area and higher chlorophyll- a: b ratio than the parent when grown in low, moderate, or high photon-flux density. Leaf thickness and leaf chlorophyll content per unit leaf area of both genotypes were less for plants grown under low irradiance, but the chlorophyll- a: b ratio was not inlfuenced by irradiance. In contrast, when grown under hot day/night temperatures of 36/29°C and high photon-flux density, the mutant exhibited similar chlorophyll content and chlorophyll composition as the parent. There was an association between higher chlorophyll content and lower, more normal, chlorophyll- a: b ratios. This association was also seen in field conditions, where the mutant produced greener leaves during hot weather in mid-summer. In sunny field conditions the mutant produced equivalent average grain-yields over 6 years, and identical biomass to the parent, even though the leaves of the mutant had substantially less chlorophyll during flowering and pod-filling. Instead of considering the mutant to be chlorophyll-deficient, it may be more appropriate to state that the parent, and many other cowpeas, have an excess of chlorophyll for growth under sunny conditions.