Chlorophyll-deficient Mutant Research Articles

Characterization and gene mapping of a chlorophyll-deficient mutant clm1 of Triticum monococcum L.

Diploid wheat Triticum monococcum L. is a model plant for wheat functional genomics. Chlorophyll-deficient mutant (clm1) was identified during manual screening of the ethyl methanesulphonate (EMS)-treated M2 progenies of T. monococcum accession pau14087 in the field. The clm1 mutant, due to significantly decreased chlorophyll content compared with the wild-type (WT), exhibited pale yellow leaves which slowly recovered to green before flowering. The clm1 mutant showed early flowering, reduced number of tillers, trichome length and density, and different shape as compared with the WT. At the same time, clm1 mutant culm had more chlorophyll-containing parenchymatous tissues compared to WT, presumably to absorb more sunlight for photosynthesis. Genetic analysis indicated that the clm1 mutation was monogenic recessive. The clm1 mutant was mapped between Xgwm473 and Xwmc96 SSR markers, with genetic distances of 2.1 and 2.6 cM, respectively, on the 7AmL chromosome.

Induction of mutation in tomato (Solanum lycopersicumL.) by gamma irradiation and EMS

Induction of mutation by gamma rays, ethyl methane sulfonate (EMS) and their combined treatments was studied in three widely divergent genotypes of tomato, EC620176, EC620177 and Patharkutchi. A steady reduction in germination percentage, seedling height and pollen fertility occurred in M1 generation with the increasing doses/concentrations of mutagens. Combination of gamma radiation and EMS caused more damage followed by EMS treatment and gamma radiation alone in M1 generation. The LD50 dose for EC620176, EC620177 and Patharkutchi corresponded to 67.3 Gy, 290.9 Gy and 303.8 Gy gamma radiation, and 0.10%, 0.17% and 0.38% EMS treatment, respectively. Highest mutation frequency was resulted by gamma radiation followed by the combined mutagens and EMS treatment. Genotype and mutagen, both, influenced the production of mutants. Mutagenic efficiency of lower doses/concentrations was more compared to higher doses in producing desirable mutants. Mutagenic effectiveness of gamma radiation was the highest followed by sole EMS and combined mutagens. Gamma irradiation (50–150 Gy) was most efficient followed by 0.05–0.10% EMS and their combination treatment in inducing wide array of macromutation in tomato. Five putative mutants with exserted stigma flower, dark green fruit, dwarf plant having pyriform fruit from Patharkutchi, multiparous cyme from EC620177 and chlorophyll deficient mutant from EC620176 that could be isolated in M2 generation hold promise for their utilization in tomato breeding programme.

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.

Truncated photosystem chlorophyll antenna size in the green microalga Chlamydomonas reinhardtii upon deletion of the TLA3-CpSRP43 gene.

The truncated light-harvesting antenna size3 (tla3) DNA insertional transformant of Chlamydomonas reinhardtii is a chlorophyll-deficient mutant with a lighter green phenotype, a lower chlorophyll (Chl) per cell content, and higher Chl a/b ratio than corresponding wild-type strains. Functional analyses revealed a higher intensity for the saturation of photosynthesis and greater light-saturated photosynthetic activity in the tla3 mutant than in the wild type and a Chl antenna size of the photosystems that was only about 40% of that in the wild type. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western-blot analyses showed that the tla3 strain was deficient in the Chl a/b light-harvesting complex. Molecular and genetic analyses revealed a single plasmid insertion in chromosome 4 of the tla3 nuclear genome, causing deletion of predicted gene g5047 and plasmid insertion within the fourth intron of downstream-predicted gene g5046. Complementation studies defined that gene g5047 alone was necessary and sufficient to rescue the tla3 mutation. Gene g5047 encodes a C. reinhardtii homolog of the chloroplast-localized SRP43 signal recognition particle, whose occurrence and function in green microalgae has not hitherto been investigated. Biochemical analysis showed that the nucleus-encoded and chloroplast-localized CrCpSRP43 protein specifically operates in the assembly of the peripheral components of the Chl a/b light-harvesting antenna. This work demonstrates that cpsrp43 deletion in green microalgae can be employed to generate tla mutants with a substantially diminished Chl antenna size. The latter exhibit improved solar energy conversion efficiency and photosynthetic productivity under mass culture and bright sunlight conditions.

A new gun mutant of oilseed rape with a reduced porphyrin flux through Mg-chelatase

Plastid-to-nucleus retrograde signaling coordinates the expression of nuclear photosynthetic genes with the developmental and functional state of the plastid. These signals are essential not only for coordinating the expression of photosynthetic genes both in the plastome and nuclear genome, but also for plants to respond optimally to environmental stress. In the present study, we found that the expression of the nuclear genes that encode plastid and non-plastid photosynthesis-related proteins was still maintained or slightly higher in cr3529, a chlorophyll deficient mutant of oilseed rape that possesses an arrested development of chloroplasts, suggesting that the expression of photosynthesis-related nuclear genes was uncoupled from the normal dependence on the developmental state of the chloroplast in cr3529. When the development of the plastid in cr3529 and the wild type was completely inhibited by lincomycin, much higher expression of photosynthesis-related nuclear genes was observed in cr3529, suggesting that the genomes uncoupled (gun) phenotype of cr3529 is even more apparent than under normal growth conditions. Lincomycin treatment also derepressed the expression of plastid genes in cr3529. The determination of porphyrin flux through Mg-chelatase showed that the content of protoporphyrin IX and Mg-protoporphyrin decreased in cr3529. The obvious gun phenotype of cr3529 under normal growth conditions and the pattern of tetrapyrrole metabolism in cr3529 suggest that it is a new gun mutant that could be used to study the regulation of the expression of nuclear and plastid genes by plastid-to-nucleus retrograde signaling under more physiological conditions and the mechanism of plant stress responses mediated by plastid signals.

Characterization of a Novel Chlorophyll-Deficient Mutant Mt6172 in Wheat

Identification of new chlorophyll-deficient mutants will provide materials for studying signaling components and pathways between plastid and nucleus. A novel chlorophyll-deficient mutant, named Mt6172, was obtained by spaceflight environment induction. Genetic analysis showed that its inheritance was controlled by nuclear and cytoplamic genes. Leaf color of its self-fertilized progenies was albino, narrow-white striped, or green. Only a few cells with abnormal chloroplasts were observed in albino plants and white section of narrow-white striped plants. These chloroplasts had obvious flaws in inner structure, and granum lamellae was extremely disordered. The narrow-white striped plants were characterized with green-and-narrow-white striped leaves, and the width of stripes between different plants was even, their plant height, number of productive tillers, and 1000-grain weight were lower than those of the wild type. The narrow-white striped plants and the wild type had significant difference in the value of potential activity of photosystem II at all tested stages. At elongation stage, which was impacted the most seriously, effective quantum yield significantly decreased, whereas the energy for photoprotection and photodamage significantly increased. Under different photosynthetic active radiation conditions, changes of electron transport rate, photochemical dissipation, and effective quantum yield were different, electron transport rate was more impacted than other parameters. Therefore, the leaf morphology and inheritance of mutant Mt6172 was different from the other reported mutants in wheat, and it was a novel mutant of chlorophyll deficiency.

Less Chlorophyll Does not Necessarily Restrain Light Capture Ability and Photosynthesis in a Chlorophyll‐Deficient Rice Mutant

AbstractA chlorophyll‐deficient rice mutant, yellow‐green leaf 1 (ygl1), with a photosynthetic rate similar to that of wild type (Oryza sativa L., cv. Zhenhui 249 China) is presented in this study. Forty percent of the chlorophyll in the mutant captured 70 % of the light in photosystem II (PSII) compared with wild type. The 30 % decreased light in the mutant was compensated for by a relatively higher quantum yield of PSII, which conferred a total electron transport rate (JT) equal to that in wild type. More photons were absorbed by wild type and exhausted through thermal dissipation. Gene expression analysis of the thylakoid membrane showed that the chlorophyll deficiency in the mutant did not impair the electron transport chain. To determine why the photosynthetic rate was similar between the chlorophyll‐deficient mutant and wild type, the leaf nitrogen (N) and Rubisco contents, stomatal and mesophyll CO2 conductance, and chloroplast development were investigated. Our results indicate that the chlorophyll deficiency in the mutant had no negative impact on the chloroplast development in terms of size and grana stacking; moreover, the chloroplastic CO2 concentration and Rubisco content were comparable to those in wild type. We conclude that the light‐capturing ability of normal rice plants is not fully utilized and that absorbed light in the chlorophyll‐deficient mutant is more efficient in participating photosynthesis.

Characteristics and molecular mapping of a novel chlorophyll-deficient yellow-leaf mutant in rice

A yellow-leaf mutant (yl11) with chlorophyll-deficient in rice (Oryza sativa L.) was selected from the progeny of a japonica rice variety "Jiahua 1" treated with 60Co γ-radiation. In comparison with the wild-type parent, "Jiahua 1", the mutant had yellow-leaves at whole growth stages and displayed significantly decreased in chlorophyll content and net photosynthetic rate. Underdeveloped chloroplast and alterations of the major agronomic traits, such as plant-heights, were also observed in the mutant. Genetic analysis confirmed that the yellow-leaf mutant trait was controlled by a single recessive nuclear gene (yl11). Using SSR and In/Del molecular markers and 920 F2 and F3 plants from the cross of yl11 with the indica variety Peiai 64S, the yl11 was mapped between the molecular markers MM2199 and InDel21039 with a physical distance of 110 kb on the long arm of chromosome 11, in which no known functional genes for chlorophyll synthesis or chloroplast development in rice has been found. These findings will provide a foundation for the cloning and functional analysis of this gene in the future.

New allele of the COCHLEATA gene in pea Pisum sativum L.

Analysis with the polymerase chain reaction showed that the Khlorofill-4 pea Pisum sativum chlorophyll-deficient mutant with reduced stipules has an altered structure of the COCHLEATA (COCH) gene, carrying a new mutant COCH allele. The phenotype of the mutant was described in comparison with another form having reduced stipules (stipules reduced) and the control. Leaves of the coch mutant are smaller and have other proportions than in the control; stipules are absent from leaves of the first nodes and are narrow, bandlike, or spoonlike at later ontogenetic stages. It was concluded that the cell number in the stipule epidermis is reduced in the st and coch mutants compared to the wild type.

Induced chlorophyll mutations. I. Mutagenic effectiveness and efficiency of EMS, HZ and SA in mungbean

A systematic and comparative study on the frequency and spectrum of chlorophyll mutations induced by ethylmethane sulphonate (EMS) — an alkylating agent, hydrazine hydrate (HZ) — a base analogue and sodium azide (SA) — a respiratory inhibitor, was carried out in two mungbean varieties, namely, PDM-11 and NM-1. Awide spectrum of chlorophyll mutants was obtained in the M2 generation. All these chlorophyll-deficient mutants were lethal except maculata, viridis and virescent. Chlorina followed by xantha types were predominant in both the varieties. EMS treatments induced the highest frequency of chlorophyll mutations followed by HZ and SA. The frequency of chlorophyll mutations was dose-dependent and increased with the mutagen concentration. Based on effectiveness in both varieties, the order of mutagens was HZ > SA > EMS. Two criteria viz., pollen sterility (Mp/S) and seedling injury (Mp/I) were taken into consideration to determine the efficiency of the mutagens. EMS was found to be the most efficient mutagen followed by HZ and SA. Moderate concentrations of the mutagens were the most effective and efficient in inducing mutations.

Effect of Colchicine Induced Mutagenesis on Growth and Yield of Sesame (<i>Sesamum indicum</i> L.)

Chemical mutagenesis through the use of colchicine on the seeds of two varieties of sesame (Sesamum indicum L. Var. Ex-Sudan and E-8) with the aim of inducing variability that could be exploited in the genetic improvement of its growth and yield was carried out. The sesame seeds were treated with colchicines at four different concentrations (0.1mM, 0.5mM, 1.0mM, 2.0mM and control) for two mutant generations (M1 and M2). Highly significant variation (P≤0.01) was observed in such quantitative traits like the germination percents, height at maturity, number of leaves produced per plant, internodes length, leaf area, number of pods/plant, number of seeds/pod and 1000 seeds weight which decreased with increase in colchicines concentrations. Besides these, a segment of chlorophyll deficient mutants such as: Chlorina, Xantha, Striata, Virescents and Lustescents were found among the mutant generations, with their frequency decreasing with increase in colchicines concentrations. Lower concentrations of colchicines were recommended for inducing genetic variability in sesame (Sesamum indicum L.) to improve the yield of such economic plant. Key words: Concentrations, Colchicines, Sesame, Ex-Sudan and E-8

Agronomic Traits and Photosynthetic Characteristics of Chlorophyll-Deficient Wheat Mutant Induced by Spaceflight Environment

Agronomic Traits and Photosynthetic Characteristics of Chlorophyll-Deficient Wheat Mutant Induced by Spaceflight Environment

Agronomic Traits and Photosynthetic Characteristics of Chlorophyll-Deficient Wheat Mutant Induced by Spaceflight Environment

Chlorophyll deficient mutants are ideal materials to study photosynthetic mechanism, pathways of chlorophyll biosynthesis and degradation, and the genes related to photosynthesis. A chlorophyll-deficient mutant of wheat ( Triticum aestivum L.), Mt135, was obtained by space mutagenesis. The main agronomic traits and photosynthetic characteristics of this mutant were compared with its wild type in field experiment. The leaf color of Mt135 showed albino, striped, and green phenotypes. The albino plants with entire albino leaves died at seedling stage. The plants with green-and-white striped leaves usually matured 5–7 d later than the wild type, and had lower plant height, shorter spike length, fewer grain number, and smaller grain weight per plant and 1000-grain weight. In contrast, the green plants of the mutant had similar agronomic traits to the wild type. Preliminary genetic analysis showed that the inheritance of leaf color in Mt135 was controlled by nucleocytoplasmic interaction. When exposed to photosynthetic active radiation (PAR) at 110 μmol m −2 s −1, the green tissue of striped plant (S-G) had a similar value of maximum photosystem II quantum yield to the wide plant, but a significantly lower potential activity of photosystem II; the photochemical quenching, nonphotochemical quenching, effective quantum yield, regulated nonphotochemical energy dissipation, and nonregulated energy dissipation varied differently at seeding, elongation, and heading stages. In addition, for electron transport rate, photochemical quenching, and effective quantum yield, the differences between S-G plant and the wild plant varied under different PAR conditions. Nevertheless, the other 2 types of the mutant, white tissue of striped plant and albino plant, showed complete losses of photosynthetic function. As a result, the photosynthesis of Mt135 was greatly restricted. High photosynthetic active radiation had tremendous impact on the mutant at elongation stage and relatively weak impact at heading stage. The changes of photosynthetic function of striped plants are in accordance with the reduction of their plant height, spike length, and yield related traits.

Optimization of ion-beam irradiation for mutagenesis in soybean: effects on plant growth and production of visibly altered mutants

Ion-beam irradiation is attracting increasing attention as a new mutagen. Here, we describe for the first time the dose response and mutagenic effects of ion-beam irradiation in soybean. We irradiated the hilum side of dried mature soybean seeds with 320-MeV carbon ions within a 0.25–20-Gy range. The growth or seed production of the irradiated plants was profoundly affected. In particular, the number of plants that survived until seed-set decreased with the increase of the irradiation dose and was very low in plants irradiated at doses higher than 5.0 Gy, whereas the frequency distribution of the number of seeds produced by each seed-setting plant was not affected by lower doses of irradiation. Based on these results, we produced plant populations irradiated at 2.5 Gy and 5.0 Gy on a large scale to obtain M2 seeds. Despite the duplicate composition of the soybean genome, which originated from tetraploids, chlorophyll-deficient mutants were detected with a frequency of 0.47% in the M2 generation of plants irradiated at 5.0 Gy. These results demonstrate that irradiation of the hilum side of dried soybean seeds with carbon-ion beams at a dose range around 2.5–5.0 Gy induces genetic changes while also allowing the production of a considerable number of seed-setting plants, suggesting that these irradiation conditions are suitable for producing a mutant population potentially useful for breeding and/or identifying gene function.

Mitochondrial activity in illuminated leaves of chlorophyll-deficient mutant rice (OsCHLH) seedlings

The rice CHLH gene encodes the Mg2+-chelatase H subunit, which is involved in chlorophyll biosynthesis. Growth of the chlorophyll-deficient oschlh mutant is supported by mitochondrial activity. In this study, we investigated the activity of mitochondrial respiration in the illuminated leaves during oschlh seedling development. Growth of mutant plants was enhanced in the presence of 3% sucrose, which may be used by mitochondria to meet cellular energy requirements. ATP content in these mutants was, however, significantly lowered in light conditions. Low cytosolic levels of NADH in illuminated oschlh mutant leaves further indicated the inhibition of mitochondrial metabolism. This down-regulation was particularly evident for oxidative stress-responsive genes in the mutant under light conditions. Hydrogen peroxide levels were higher in oschlh mutant leaves than in wild-type leaves; this increase was largely caused by the impairment of the expression of the antioxidant genes, such as OsAPX1, OsRAC1, and OsAOXc in knockout plants. Moreover, treatment of mesophyll protoplasts with ascorbic acid or catalase recovered ATP content in the mutants. Taken together, these results suggest that the light-mediated inhibition of mitochondrial activity leads to stunted growth of CHLH rice seedlings.

Identification of differentially expressed proteins of a new rice mutant with albino green-revertible trait in the seedling stage

Chlorophyll-deficient mutants have been employed to study the mechanism of chlorophyll and chloroplast biogenesis in plants. We found a new chlorophyll-deficient mutant rice line (W02S) whose leaves, unlike those of its isogenic line (Peiai64S), became etiolated at the two-leaf stage and turned green at the three-leaf stage. 2-D gel electrophoresis was performed, and proteins that were differentially expressed between W02S and Peiai64S were selected for MALDI-TOF MS analysis. A total of 44 highly differentially expressed proteins were collected from the two-leaf stage of W02S. These 44 proteins can be classified into 10 categories, 15 were novel and unknown functional proteins, 6 proteins participated in the EMP-TCA-ETC pathway, and 4 proteins were involved in the in signal transduction. Four representative protein spots were selected for real-time quantitative PCR analysis. The mRNA levels of three genes encoding an enolase, a chloroplast 29 kDa ribonucleoprotein and a proteasome alpha subunit were significantly increased in the samples from the two-leaf stage of W02S, indicating that a substantial proportion of protein changes is the consequence of altered mRNA levels during the seedling stages of the mutant rice. These findings provide new insights into the mechanisms for chlorophyll-deficient mutant rice and other plants as well.Key words: Oryza sativa L., 2-D gel , real time PCR, chlorophyll-deficient mutant

Correlation of electronic carotenoid–chlorophyll interactions and fluorescence quenching with the aggregation of native LHC II and chlorophyll deficient mutants

The aggregation dependent correlation between fluorescence quenching and the electronic carotenoid–chlorophyll interactions, ϕ Coupling Car S 1 - Chl , as measured by comparing chlorophyll fluorescence observed after two- and one-photon excitation, has been investigated using native LHC II samples as well as mutants lacking Chl 2 and Chl 13. For native LHC II the same linear correlation between ϕ Coupling Car S 1 - Chl and the fluorescence quenching was observed as previously reported for the pH and Zea-dependent quenching of LHC II [1]. In order to elucidate which carotenoid–chlorophyll pair might dominate this correlation we also investigated the mutants lacking Chl 2 and Chl 13. However, also with these mutants the same linear correlation as for native LHC II was observed. This provides indication that these two chlorophylls play only a minor role for the observed effects. Nevertheless, we also conclude that this does not exclude that their neighboured carotenoids, lutein 1 and neoxanthin, might interact electronically with other chlorophylls close by.

A Cytoplasmically Inherited Barley Mutant Is Defective in Photosystem I Assembly Due to a Temperature-Sensitive Defect in ycf3 Splicing

A cytoplasmically inherited chlorophyll-deficient mutant of barley (Hordeum vulgare) termed cytoplasmic line 3 (CL3), displaying a viridis (homogeneously light-green colored) phenotype, has been previously shown to be affected by elevated temperatures. In this article, biochemical, biophysical, and molecular approaches were used to study the CL3 mutant under different temperature and light conditions. The results lead to the conclusion that an impaired assembly of photosystem I (PSI) under higher temperatures and certain light conditions is the primary cause of the CL3 phenotype. Compromised splicing of ycf3 transcripts, particularly at elevated temperature, resulting from a mutation in a noncoding region (intron 1) in the mutant ycf3 gene results in a defective synthesis of Ycf3, which is a chaperone involved in PSI assembly. The defective PSI assembly causes severe photoinhibition and degradation of PSII.

Identification of Differentially Expressed Proteins Associated with Chlorophyll-Deficient Mutant Rice

Identification of Differentially Expressed Proteins Associated with Chlorophyll-Deficient Mutant Rice

Identification and fine mapping of a thermo-sensitive chlorophyll deficient mutant in rice (Oryza sativa L.)

A thermo-sensitive chlorophyll deficient mutant was isolated from more than 15,000 transgenic rice lines. The mutant displayed normal phenotype at 23 degrees C or lower temperature (permissive temperature). However, when grown at 26 degrees C or higher (nonpermissive temperature) the plant exhibited an abnormal phenotype characterized by yellow green leaves. Genetic analysis revealed that a single nuclear-encoded recessive gene is responsible for the mutation, which is tentatively designed as cde1(t) (chlorophyll deficient 1, temporally). PCR analysis and hygromycin resistance assay indicated the mutation was not caused by T-DNA insertion. To isolate the cde1(t) gene, a map-based cloning strategy was employed and 15 new markers (five SSR and ten InDels markers) were developed. A high-resolution physical map of the chromosomal region around the cde1(t) gene was made using F(2) and F(3) population consisting of 1,858 mutant individuals. Finally, the cde1(t) gene was mapped in 7.5 kb region between marker ID10 and marker ID11 on chromosome 2. Sequence analysis revealed only one candidate gene, OsGluRS, in the 7.5 kb region. Cloning and sequencing of the target region from the cde1(t) mutant showed that a missense mutation occurred in the mutant. So the OsGluRS gene (TIGR locus Os02 g02860) which encode glutamyl-tRNA synthetase was identified as the Cde1(t) gene.