Defect in Brnym1, a magnesium-dechelatase protein, causes a stay-green phenotype in an EMS-mutagenized Chinese cabbage (Brassica campestris L. ssp. pekinensis) line

AbstractLeaf color is an important target trait in Chinese cabbage breeding programs. Leaf yellowing may reduce crop commercial and nutritional values. Some plants with the “stay-green” trait maintain leaf greenness during senescence and even after death. Stay-green Chinese cabbage may be a focal point of future breeding projects because it could improve crop quality and yield and prolong shelf life. A new stay-green mutant, non-yellowing mutant 1 (nym1), was identified in Chinese cabbage derived from an ethyl methane sulfonate (EMS)-mutagenized population. The mutant had stay-green characteristics and a higher chlorophyll content than the wild-type during leaf senescence. The stay-green trait in the mutant Chinese cabbage was controlled by the recessive gene Brnym1. MutMap and KASP analyses showed that Brnym1 (BraA03g050600.3C) encodes an mg-dechelatase (SGR protein), which might be the causal gene of the mutation in Chinese cabbage. A nonsynonymous single nucleotide base substitution (G to A) in the third exon of Brnym1 caused an amino acid substitution from L to F in the highly conserved domain of the magnesium-dechelatase. Ectopic overexpression showed that the BrNYM1 gene of wild-type Chinese cabbage complemented the SGR-defective stay-green mutant nye1-1 of Arabidopsis. The magnesium-dechelatase activity in the nym1 mutant was significantly downregulated compared to that in the wild type. Brnym1 was relatively upregulated in the mutant during late senescence, and BrNYM1 was localized to the chloroplasts. These results indicate that Brnym1 (BraA03g050600.3C) is the causal gene of the stay-green mutation and could be of particular significance in the genetic improvement of Chinese cabbage.

Download Full-text

The mutation of ent-kaurene synthase, a key enzyme involved in gibberellin biosynthesis, confers a non-heading phenotype to Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Horticulture Research ◽

10.1038/s41438-020-00399-6 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Yue Gao ◽

Shengnan Huang ◽

Gaoyang Qu ◽

Wei Fu ◽

Meidi Zhang ◽

...

Keyword(s):

Chinese Cabbage ◽

Recessive Gene ◽

Gibberellin Biosynthesis ◽

Wild Type ◽

Specific Pcr ◽

Head Development ◽

Nucleotide Mutation ◽

In The Wild ◽

Leafy Head ◽

Heading Chinese Cabbage

Abstract The presence of a leafy head is a vital agronomic trait that facilitates the evaluation of the yield and quality of Chinese cabbage. A non-heading mutant (nhm1) was identified in an ethyl methanesulfonate mutagenesis population of the heading Chinese cabbage double haploid line FT. Segregation analysis revealed that a single recessive gene, Brnhm1, controlled the mutant phenotype. Using MutMap, Kompetitive allele-specific PCR, and cloning analyses, we demonstrated that BraA07g042410.3C, which encodes an ent-kaurene synthase involved in the gibberellin biosynthesis pathway, is the nhm1 mutant candidate gene. A single-nucleotide mutation (C to T) in the fourth exon of BraA07g042410.3C caused an amino acid substitution from histidine to tyrosine. Compared to that of the wild-type FT, BraA07g042410.3C in the leaves of the nhm1 mutant had lower levels of expression. In addition, gibberellin contents were lower in the mutant than in the wild type, and the mutant plant phenotype could be restored to that of the wild type after exogenous GA3 treatment. These results indicate that BraA07g042410.3C caused the non-heading mutation. This is the first study to demonstrate a relationship between gibberellin content in the leaves and leafy head formation in Chinese cabbage. These findings facilitate the understanding of the mechanisms underlying leafy head development in Chinese cabbage.

Download Full-text

Use of mutants to establish (+)-scytalone as an intermediate in melanin biosynthesis by Verticillium dahliae

Canadian Journal of Microbiology ◽

10.1139/m76-115 ◽

1976 ◽

Vol 22 (6) ◽

pp. 787-799 ◽

Cited By ~ 70

Author(s):

A. A. Bell ◽

J. E. Puhalla ◽

W. J. Tolmsoff ◽

R. D. Stipanovic

Keyword(s):

Physical Properties ◽

Verticillium Dahliae ◽

Recessive Gene ◽

The Other ◽

Thielaviopsis Basicola ◽

Single Recessive Gene ◽

Wild Type ◽

Melanin Biosynthesis ◽

In The Wild ◽

Verticillium Dahliae Kleb

Melanin biosynthesis in Verticillium dahliae Kleb. was studied with mutants deficient for normal black melanin or for production of microsclerotia. Seven genetically different mutants had apparent blocks in melanin biosynthesis. Four mutants (brm-I to -4) produced brown microsclerotia and extruded pigments into media; three (alm-1 to -3) produced albino microsclerotia. Other mutants produced no microsclerotia (nms) or had greatly reduced numbers of microsclerotia (rms). Mutation alm-1 was due to a single recessive gene; the other melanin-deficient characters were recessive but their genetic bases were not determined. Cultures of the brown mutants brm-1 and -3 extruded and accumulated a metabolite that blackened the albino microsclerotia of alm-1 to -3. The metabolite was identified as (+)-scytalone (3, 4-dihydro-3, 6, 8-trihydroxy-1(2H)naphthalenone). Pigment formed by alm-1 microsclerotia from (+)-scytalone had chemical and physical properties identical with those of melanin in the wild-type fungus. (+)-Scytalone was produced and converted to melanin by microsclerotia but not by conidia or hyphae. Conversion of (+)-scytalone to melanin appeared to involve two or more enzymes and probably involved conversions to 1, 3, 8-trihydroxynaphthalene and 1, 8-dihydroxynaphthalene. Albino mutants of Thielaviopsis basicola, Drechslera sorokiniana, Pleospora infectoria (Alternaria), Ulocladium sp., and Curvularia sp. also converted scytalone to pigments indistinguishable from the melanins found in their respective wild types. Scytalone melanin may be common in fungi with dark brown or black pigments.

Download Full-text

Ripening Characteristics and Pigment Changes in Russeted Pear Fruit in Response to Ethylene and 1-MCP

Horticulturae ◽

10.3390/horticulturae4030022 ◽

2018 ◽

Vol 4 (3) ◽

pp. 22 ◽

Cited By ~ 3

Author(s):

Nongluk Charoenchongsuk ◽

Daiki Matsumoto ◽

Akihiro Itai ◽

Hideki Murayama

Keyword(s):

Ethylene Production ◽

Chlorophyll Degradation ◽

Fruit Softening ◽

Wild Type ◽

Pear Fruit ◽

Pheophorbide A ◽

Stay Green ◽

In The Wild ◽

Chlorophyll Level ◽

Pheophorbide A Oxygenase

Ripening characteristics and pigment changes were investigated in ‘La France’, ‘Gorham’, and their russeted sports ‘Gold La France’ and ‘Grand Champion’ pears. Fruit were harvested at commercial maturity and ripened at 20 °C. In all cultivars, fruit softening was concomitant with a burst in ethylene production. Interestingly, such changes were delayed in russet pear when compared with their wild-types. Chlorophyll level in russet pear at harvest was the same as in the wild-type. In ‘Gorham’ and ‘Grand Champion’ pears, its level rapidly decreased during ripening. Ethylene or 1-methylcyclopropene (1-MCP) did not affect the color and pigments in ‘La France’ and ‘Gold La France’ pears. In contrast, in ‘Gorham’ and ‘Grand Champion’ pears, chlorophyll degradation was suppressed by 1-MCP treatment, but not completely. These results suggested that chlorophyll degradation was regulated by both ethylene-dependent and ethylene-independent means. The influence of ethylene on the expression of chlorophyll-degradation-related genes seemed to be similar in both russet and wild-type. The Stay green-1 gene was stimulated by ethylene and suppressed by 1-MCP treatment. In contrast, little effect of ethylene or 1-MCP was observed on chlorophyllase 1, pheophytinase, pheophorbide a oxygenase, and NYC1-like genes.

Download Full-text

Elevated Mutation Frequency in Surviving Populations of Carbon-Starved rpoS-Deficient Pseudomonas putida Is Caused by Reduced Expression of Superoxide Dismutase and Catalase

Journal of Bacteriology ◽

10.1128/jb.01803-08 ◽

2009 ◽

Vol 191 (11) ◽

pp. 3604-3614 ◽

Cited By ~ 12

Author(s):

Kairi Tarassova ◽

Radi Tegova ◽

Andres Tover ◽

Riho Teras ◽

Mariliis Tark ◽

...

Keyword(s):

Superoxide Dismutase ◽

Oxidative Damage ◽

Pseudomonas Putida ◽

Mutation Frequency ◽

Test System ◽

Base Substitution ◽

Repair System ◽

Wild Type ◽

Large Deletions ◽

In The Wild

ABSTRACTRpoS is a bacterial sigma factor of RNA polymerase which is involved in the expression of a large number of genes to facilitate survival under starvation conditions and other stresses. The results of our study demonstrate that the frequency of emergence of base substitution mutants is significantly increased in long-term-starved populations ofrpoS-deficientPseudomonas putidacells. The increasing effect of the lack of RpoS on the mutation frequency became apparent in both a plasmid-based test system measuring Phe+reversion and a chromosomalrpoBsystem detecting rifampin-resistant mutants. The elevated mutation frequency coincided with the death of about 95% of the cells in a population ofrpoS-deficientP.putida. Artificial overexpression of superoxide dismutase or catalase in therpoS-deficient strain restored the survival of cells and resulted in a decline in the mutation frequency. This indicated that, compared to wild-type bacteria,rpoS-deficient cells are less protected against damage caused by reactive oxygen species. 7,8-Dihydro-8-oxoguanine (GO) is known to be one of the most stable and frequent base modifications caused by oxygen radical attack on DNA. However, the spectrum of base substitution mutations characterized inrpoS-deficientP.putidawas different from that in bacteria lacking the GO repair system: it was broader and more similar to that identified in the wild-type strain. Interestingly, the formation of large deletions was also accompanied by a lack of RpoS. Thus, the accumulation of DNA damage other than GO elevates the frequency of mutation in these bacteria. It is known that oxidative damage of proteins and membrane components, but not that of DNA, is a major reason for the death of cells. Since the increased mutation frequency was associated with a decline in the viability of bacteria, we suppose that the elevation of the mutation frequency in the surviving population of carbon-starvedrpoS-deficientP.putidamay be caused both by oxidative damage of DNA and enzymes involved in DNA replication and repair fidelity.

Download Full-text

Freeze-substituted fungal cells of Nectria haematococca: A comparison of the macroconidial walls of the adhesion-competent wild type with an adhesion-reduced mutant

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100160996 ◽

1990 ◽

Vol 48 (3) ◽

pp. 688-689

Author(s):

Thecan Caesar-Ton That ◽

Lynn Epstein

Keyword(s):

Freeze Substitution ◽

Uranyl Acetate ◽

Wild Type ◽

Nectria Haematococca ◽

Fruit Extract ◽

Dialysis Tubing ◽

Tube Emergence ◽

Contrast Microscopy ◽

In The Wild ◽

Freeze Damage

Nectria haematococca mating population I (anamorph, Fusarium solani) macroconidia attach to its host (squash) and non-host surfaces prior to germ tube emergence. The macroconidia become adhesive after a brief period of protein synthesis. Recently, Hickman et al. (1989) isolated N. haematococca adhesion-reduced mutants. Using freeze substitution, we compared the development of the macroconidial wall in the wild type in comparison to one of the mutants, LEI.Macroconidia were harvested at 1C, washed by centrifugation, resuspended in a dilute zucchini fruit extract and incubated from 0 - 5 h. During the incubation period, wild type macroconidia attached to uncoated dialysis tubing. Mutant macroconidia did not attach and were collected on poly-L-lysine coated dialysis tubing just prior to freezing. Conidia on the tubing were frozen in liquid propane at 191 - 193C, substituted in acetone with 2% OsO4 and 0.05% uranyl acetate, washed with acetone, and flat-embedded in Epon-Araldite. Using phase contrast microscopy at 1000X, cells without freeze damage were selected, remounted, sectioned and post-stained sequentially with 1% Ba(MnO4)2 2% uranyl acetate and Reynold’s lead citrate. At least 30 cells/treatment were examined.

Download Full-text

Rad51-Independent Interchromosomal Double-Strand Break Repair by Gene Conversion Requires Rad52 but Not Rad55, Rad57, or Dmc1

Molecular and Cellular Biology ◽

10.1128/mcb.00524-07 ◽

2007 ◽

Vol 28 (3) ◽

pp. 897-906 ◽

Cited By ~ 21

Author(s):

Thomas J. Pohl ◽

Jac A. Nickoloff

Keyword(s):

Gene Conversion ◽

Strand Break ◽

Double Strand Break ◽

Single Strand ◽

Homology Search ◽

Wild Type ◽

Dsb Repair ◽

Single Strand Annealing ◽

In The Wild ◽

Break Induced Replication

ABSTRACT Homologous recombination (HR) is critical for DNA double-strand break (DSB) repair and genome stabilization. In yeast, HR is catalyzed by the Rad51 strand transferase and its “mediators,” including the Rad52 single-strand DNA-annealing protein, two Rad51 paralogs (Rad55 and Rad57), and Rad54. A Rad51 homolog, Dmc1, is important for meiotic HR. In wild-type cells, most DSB repair results in gene conversion, a conservative HR outcome. Because Rad51 plays a central role in the homology search and strand invasion steps, DSBs either are not repaired or are repaired by nonconservative single-strand annealing or break-induced replication mechanisms in rad51Δ mutants. Although DSB repair by gene conversion in the absence of Rad51 has been reported for ectopic HR events (e.g., inverted repeats or between plasmids), Rad51 has been thought to be essential for DSB repair by conservative interchromosomal (allelic) gene conversion. Here, we demonstrate that DSBs stimulate gene conversion between homologous chromosomes (allelic conversion) by >30-fold in a rad51Δ mutant. We show that Rad51-independent allelic conversion and break-induced replication occur independently of Rad55, Rad57, and Dmc1 but require Rad52. Unlike DSB-induced events, spontaneous allelic conversion was detected in both rad51Δ and rad52Δ mutants, but not in a rad51Δ rad52Δ double mutant. The frequencies of crossovers associated with DSB-induced gene conversion were similar in the wild type and the rad51Δ mutant, but discontinuous conversion tracts were fivefold more frequent and tract lengths were more widely distributed in the rad51Δ mutant, indicating that heteroduplex DNA has an altered structure, or is processed differently, in the absence of Rad51.

Download Full-text

Effects of Mutations of RAD50, RAD51, RAD52, and Related Genes on Illegitimate Recombination in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/142.2.383 ◽

1996 ◽

Vol 142 (2) ◽

pp. 383-391 ◽

Cited By ~ 2

Author(s):

Yasumasa Tsukamoto ◽

Jun-ichi Kato ◽

Hideo Ikeda

Keyword(s):

Saccharomyces Cerevisiae ◽

Quantitative Analysis ◽

Structural Analysis ◽

Recombination Rate ◽

Type Strain ◽

Negative Selection ◽

Wild Type Strain ◽

Illegitimate Recombination ◽

Wild Type ◽

In The Wild

Abstract To examine the mechanism of illegitimate recombination in Saccharomyces cerevisiae, we have developed a plasmid system for quantitative analysis of deletion formation. A can1 cyh2 cell carrying two negative selection markers, the CAN1 and CYH2 genes, on a YCp plasmid is sensitive to canavanine and cycloheximide, but the cell becomes resistant to both drugs when the plasmid has a deletion over the CAN1 and CYH2 genes. Structural analysis of the recombinant plasmids obtained from the resistant cells showed that the plasmids had deletions at various sites of the CAN1-CYH2 region and there were only short regions of homology (1-5 bp) at the recombination junctions. The results indicated that the deletion detected in this system were formed by illegitimate recombination. Study on the effect of several rad mutations showed that the recombination rate was reduced by 30-, 10-, 10-, and 10-fold in the rad52, rad50, mre11, and xrs2 mutants, respectively, while in the rud51, 54, 55, and 57 mutants, the rate was comparable to that in the wild-type strain. The rad52 mutation did not affect length of homology at junction sites of illegitimate recombination.

Download Full-text

Developing a Genetic System in Deinococcus radiodurans for Analyzing Mutations

Genetics ◽

10.1093/genetics/166.2.661 ◽

2004 ◽

Vol 166 (2) ◽

pp. 661-668

Author(s):

Mandy Kim ◽

Erika Wolff ◽

Tiffany Huang ◽

Lilit Garibyan ◽

Ashlee M Earl ◽

...

Keyword(s):

Dna Sequences ◽

Deinococcus Radiodurans ◽

Genetic System ◽

Base Change ◽

Base Substitution ◽

Wild Type ◽

Base Pairs ◽

E Coli ◽

Radiation Induced ◽

Induced Mutagenesis

Abstract We have applied a genetic system for analyzing mutations in Escherichia coli to Deinococcus radiodurans, an extremeophile with an astonishingly high resistance to UV- and ionizing-radiation-induced mutagenesis. Taking advantage of the conservation of the β-subunit of RNA polymerase among most prokaryotes, we derived again in D. radiodurans the rpoB/Rif r system that we developed in E. coli to monitor base substitutions, defining 33 base change substitutions at 22 different base pairs. We sequenced >250 mutations leading to Rif r in D. radiodurans derived spontaneously in wild-type and uvrD (mismatch-repair-deficient) backgrounds and after treatment with N-methyl-N′-nitro-N-nitrosoguanidine (NTG) and 5-azacytidine (5AZ). The specificities of NTG and 5AZ in D. radiodurans are the same as those found for E. coli and other organisms. There are prominent base substitution hotspots in rpoB in both D. radiodurans and E. coli. In several cases these are at different points in each organism, even though the DNA sequences surrounding the hotspots and their corresponding sites are very similar in both D. radiodurans and E. coli. In one case the hotspots occur at the same site in both organisms.

Download Full-text

Transcriptome Analysis Provides Insights into the Mechanism of Astaxanthin Enrichment in a Mutant of the Ridgetail White Prawn Exopalaemon carinicauda

Genes ◽

10.3390/genes12050618 ◽

2021 ◽

Vol 12 (5) ◽

pp. 618

Author(s):

Yue Jin ◽

Shihao Li ◽

Yang Yu ◽

Chengsong Zhang ◽

Xiaojun Zhang ◽

...

Keyword(s):

Transcriptome Analysis ◽

Underlying Mechanism ◽

Biological Processes ◽

Wild Type ◽

Expression Levels ◽

In The Wild ◽

Cuticle Proteins ◽

Apolipoprotein D ◽

High Level ◽

Lower Expression

A mutant of the ridgetail white prawn, which exhibited rare orange-red body color with a higher level of free astaxanthin (ASTX) concentration than that in the wild-type prawn, was obtained in our lab. In order to understand the underlying mechanism for the existence of a high level of free astaxanthin, transcriptome analysis was performed to identify the differentially expressed genes (DEGs) between the mutant and wild-type prawns. A total of 78,224 unigenes were obtained, and 1863 were identified as DEGs, in which 902 unigenes showed higher expression levels, while 961 unigenes presented lower expression levels in the mutant in comparison with the wild-type prawns. Based on Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes analysis, as well as further investigation of annotated DEGs, we found that the biological processes related to astaxanthin binding, transport, and metabolism presented significant differences between the mutant and the wild-type prawns. Some genes related to these processes, including crustacyanin, apolipoprotein D (ApoD), cathepsin, and cuticle proteins, were identified as DEGs between the two types of prawns. These data may provide important information for us to understand the molecular mechanism of the existence of a high level of free astaxanthin in the prawn.

Download Full-text

cot1: A Regulator of Arabidopsis Trichome Initiation

Genetics ◽

10.1093/genetics/149.2.565 ◽

1998 ◽

Vol 149 (2) ◽

pp. 565-577

Author(s):

Daniel B Szymanski ◽

Daniel A Klis ◽

John C Larkin ◽

M David Marks

Keyword(s):

Cell Fate ◽

Gene Dosage ◽

Signal Transduction Pathway ◽

Spatial Arrangement ◽

Complex Signal ◽

Chromosome 2 ◽

Wild Type ◽

Trichome Formation ◽

In The Wild ◽

Leaf Trichome

Abstract In Arabidopsis, the timing and spatial arrangement of trichome initiation is tightly regulated and requires the activity of the GLABROUS1 (GL1) gene. The COTYLEDON TRICHOME 1 (COT1) gene affects trichome initiation during late stages of leaf development and is described in this article. In the wild-type background, cot1 has no observable effect on trichome initiation. GL1 overexpression in wild-type plants leads to a modest number of ectopic trichomes and to a decrease in trichome number on the adaxial leaf surface. The cot1 mutation enhances GL1-overexpression-dependent ectopic trichome formation and also induces increased leaf trichome initiation. The expressivity of the cot1 phenotype is sensitive to cot1 and 35S::GL1 gene dosage, and the most severe phenotypes are observed when cot1 and 35S::GL1 are homozygous. The COT1 locus is located on chromosome 2 15.3 cM north of er. Analysis of the interaction between cot1, try, and 35S::GL1 suggests that COT1 is part of a complex signal transduction pathway that regulates GL1-dependent adoption of the trichome cell fate.

Download Full-text