Male Sterile Phenotype Research Articles

Genetic basis of X-Y chromosome dissociation and male sterility in interspecific hybrids.

A high frequency of X-Y chromosome dissociation (95%) was found at first meiotic metaphase (MI) in spermatocytes of interspecific hybrids between laboratory mice, C57BL/6J (BL/6) and Mus spretus, compared with an X-Y dissociation frequency of only 3-4% in parental mice. The X-Y dissociation in F1 hybrids occurred before diakinesis rather than as a precocious dissociation at MI. The high X-Y dissociation was accompanied by spermatogenic breakdown after MI, resulting in male sterility. All F1 males were sterile and approximately half of the backcross males from fertile F1 females crossed with either BL/6 or M. spretus males were sterile. Male sterility was highly correlated with X-Y dissociation in both backcrosses. All of the mice with high X-Y dissociation were sterile and all of the males with low X-Y dissociation were fertile or subfertile. This correlation suggested that genetic divergence of the X-Y pairing region could contribute to the male sterile phenotype such that the BL/6 X chromosome would not pair with the M. spretus Y chromosome. The segregation of species-type alleles of amelogenin (Amelb and Amels), a distal X chromosome locus adjacent to the X-Y pairing region, was followed in backcross males that were analyzed for X-Y dissociation and sterility (we have used Amel as the designation for the mouse amelogenin locus; the current designation for this locus is Amg). A 95% concordance between Amelb with fertility and Amels with sterility was observed in backcrosses with BL/6, whereas the converse was observed in the backcross to M. spretus. These results imply that X-Y pairing plays an important role in male fertility and suggest that genetic divergence in X-Y pairing region between Mus species can contribute to the reproductive barriers between species and the process of speciation.

Expression in Saccharomyces cerevisiae of a gene associated with cytoplasmic male sterility from maize: Respiratory dysfunction and uncoupling of yeast mitochondria

We asked whether the mitochondrial T-urf13 gene, associated with the male sterility phenotype of T cytoplasm in maize, can be expressed in Saccharomyces cerevisiae and whether this expression can mimic the effects observed in maize. We introduced the universal code equivalent of the T-urf13 gene into the S. cerevisiae nucleus by transformation and directed its translation product into mitochondria by means of a fusion with the targeting presequence from Neurospora crassa AT-Pase subunit 9. We show that expression of the universal code equivalent of the T-urf13 gene in the yeast nucleus does indeed mimic its effects in maize: respiratory growth of yeast is inhibited, respiration-deficient cytoplasmic mutants accumulate and NADH oxidation of isolated mitochondria is uncoupled. All these effects are observed only if the mitochondrial targeting peptide and methomyl or HmT toxin are present.

Modifications of floral development in tobacco induced by fusion of protoplasts of different male-sterile cultivars

Protoplasts derived from different cytoplasmic male-sterile cultivars of Nicotiana tabacum were fused. Nearly 200 cybrid calli were regenerated into plants and their flower morphologies were examined. Most cybrids exhibited parental-type male-sterile morphologies. Some, however, showed novel male-sterile phenotypes or phenotypes which combined traits of both male-sterile parents in a new combination. Others were restored to fertility, with stamens which produced functional pollen.

Comparison of the organization and expression of mtDNA of fertile and male-sterile sugar beet varieties (Beta vulgaris L.)

Analysis of minicircle occurrence in different samples of sugar beet mitochondrial (mt) DNA invalidates the postulated relationship between cytoplasmic male sterility (CMS) phenotype and the absence of minicircle c and d. In high molecular weight mt DNA, two types of restriction patterns are found for fertile genomes and only one type for the CMS; in spite of the multiplicity of crosses carried out by plant breeders, all the CMS varieties analyzed seem to have derived from the original cytoplasm discovered by Owen in 1945. Southern hybridizations with mitochondrial genes coding for cytochrome oxidase subunits II and III, ATPase subunits α, 6 and 9 and 26S ribosomal RNA indicate that gene organization is different between fertile and sterile genomes but similar in all fertile genomes. Transcription analysis with the same genes indicate several differences between fertile and sterile varieties but also within some fertile varieties. These results suggest that the mt genome found in male-sterile sugar beet may originate not from modifications of the fertile mitochondrial genome but from a particular source of cytoplasm, of which a possible origin is discussed.

Gynodioecy in Plantago lanceolata. VI. Functions of cytokinins in growth, development, and reproduction of two sex types

Theoretical models predict that male sterile plants of gynodioecious species should show at least some compensation for their disadvantage of not reproducing as males through female component of fitness, In this study, growth, development, and reproduction of a hermaphrodite and a male sterile family of Plantago lanceolata L. were compared under controlled conditions. The male sterile plants produced more and longer spikes and had relatively longer styles. The male sterile plants achieved their final biomass sooner, by an earlier formation of side rosettes, and flowered earlier. The hypothesis was tested as to whether cytokinins in the plants are involved as a pleiotropic factor in either or both sex expression and the various plant characteristics associated with the male sterile phenotype. The roots of the male sterile plants had higher concentrations of putative zeatin riboside than the roots of the hermaphroditic plants, as quantified by an enzyme-linked immunoassy after separation of cytokinins by high performance liquid chromatography. Spraying the plants with benzyladenine did not affect internal cytokinin concentrations or sex expression. Benzyladenine spray increased the growth rate of the main rosette and stimulated floral initiation. Our results indicate that cytokinins are possibly involved in determining the morphological differences between sex types in this species.

Molecular and genetic organization of the suppressor of sable and minute (1) 1B region in Drosophila melanogaster.

Recessive mutations at the suppressor of sable [su(s)] locus in Drosophila melanogaster result in suppression of second site mutations caused by insertions of the mobile element 412. In order to determine whether su(s) mutations might have other phenotypes, a saturation mapping of the su(s) region was carried out. The screen yielded 76 mutations that comprise ten genetic complementation groups ordered distal to proximal as follows: l(1)1Bh, l(1)1Bi, M(1)1B, su(s), l(1)1Bk, l(1)1Ca, mul, tw, l(1)lDa and brc. Twenty-three of the mutations are su(s) alleles, and all are suppressors of the 412-insertion-caused v1 allele. Although the screen could have detected su(s) mutations causing sex-specific dominant lethality or sterility as well as all types of recessive lethality or sterility, the only other phenotype observed was male sterility that is enhanced by cold temperature. This type of sterility is exhibited only by alleles induced by base-substitution-causing mutagens. Genetic functions of the poly(A+) messages transcribed from the su(s) microregion were identified by the reintroduction of cloned sequences into embryos by P element transformation. su(s) function has been attributed to a 5-kb message. The segment of DNA encoding only this 5-kb message rescues both the suppression and cold-sensitive male sterility phenotypes of su(s). Minute (1) 1B has been provisionally identified as encoding a 3.5-kb message; lethal (1)1Bi encodes a 1-kb message; and lethal (1)1Bk encodes a 4-kb message. The possible functions of su(s) and M(1)1B are discussed.

Allelic relationship of four male sterility genes and nucleo-cytoplasmic interactions in the expression of male sterility in pearl millet, Pennisetum americanum (L.) leeke

Male sterility genes isolated in four inbred lines of pearl millet were found allelic. The differences between male fertile and male sterile phenotypes is mainly due to a single gene. Presence of a dominant gene (Ms) resulted in male fertility and double recessiveness (ms ms) in male sterility. However, genic male sterility (GMS) in Pennisetum is not a simply inherited case of monogenic recessive condition but is influenced by cytoplasmic and several nuclear factors. In a male sterile, the stage at which the male sterility gene is expressed during the development of the male gametophyte resulting in breakdown of the cells is influenced by cytoplasmic and other nuclear factors. Two types of cytoplasm, C-1 and C-2, are recognized. Presence of any two recessive male sterility alleles in C-1 led to breakdown of male development before differentiation of an archesporium in the anther (Arc-type); in C-2 cytoplasm, degeneration started during meiosis with fusion of meiocytes and syncyte formation (Syn-type), or at post-meiotic stages terminating in abortion of microspores before first pollen mitosis (PGM type). The triggering of activity of recessive male sterility genes in C-2 cytoplasm appeared to be regulated by two nuclear factors, R 1 and R 2 with duplicate gene action. Recessiveness for both the R factors in C-2 cytoplasm resulted in PGM-type expression. The action of R 1 and R 2 is specific to C-2 cytoplasm. Mutation of cytoplasm from C-1 to C-2 and C-2 to C-1 was observed.

An S1 episomal gene of maize mitochondria is expressed in male sterile and fertile plants of the S-type cytoplasm

Maize mitochondria of cytoplasmic male sterile (cms-S) plants contain two linear episomes, S1 (6397 bp) and S2 (5453 bp). S1 contains three long open reading frames URF2 (1017 bp), URF3 (2782 bp) and URF4 (768 bp). We have demonstrated that the URF3 sequence of S1 encodes a protein with an apparent molecular weight of 103 kDa which is found in cms-S but undetectable in cms-T, cms-C or normal (fertile) mitochondria. A translational fusion containing the 5′ terminus of the lacZ gene and 800 bp of the 3′ end of URF3 was isolated from a cms-S mitochondrial genomic library in the expression vector λgt11. Polyclonal antibodies raised against the resulting fusion protein immunoprecipitated a 103 kDa polypeptide from among [35S]-methionine-labeled cms-S mitochondrial proteins but not from normal mitochondrial proteins. The mitochondria of fertile F1 plants resulting from a cross between B37 cms-S and Ky21 (universal restorer) contain as much of this 103 kDa protein as is observed in sterile cms-S mitochondria. The mitochondria of fertile cytoplasmic revertants from cms-RD and cms-LM in a WF9 nuclear background also synthesized the 103 kDa protein. We conclude that the URF3 sequence of the S1 episome is expressed in vivo and that the presence of its gene product in maize mitochondria is not sufficient to confer the male sterile phenotype.

Male sterility caused by p6H and qk mutations is not corrected in chimeric mice.

It is not known if the male sterility caused by the pleiotropic mutations p6H (pink-eyed 6H) and qk (quaking) is intrinsic or extrinsic to spermatogenic cells. This question was addressed by juxtaposing mutant and normal cells in the testes of chimeric mice and determining whether the mutant germ cells could form functional sperm. Twenty-one male chimeras consisting of normal cells and p6H/p6H or qk/qk cells were analyzed. For each, breeding productivity and testicular and sperm morphology were determined. Karyotypes and isozyme analyses were performed to identify the two cellular components of each chimera. All male chimeras that contained p6H/p6H, XY cells were sterile. Although some chimeras with a qk/qk, XY mutant component were fertile, none produced offspring from the homozygous qk component. Spermatids of the sterile chimeras showed abnormalities characteristic of the mutations. We conclude from this study that the presence of normal XY germ and somatic cells in the testis did not rescue the male sterile phenotype of homozygous p6H or qk XY germ cells. Therefore, the action of these mutant genes in causing sperm abnormalities and sterility is autonomous to the germ cells.

Nuclear-mitochondrial interactions in cytoplasmic male-sterile sorghum

Variation in mitochondrial genome organization and expression between male fertile and sterile nuclear-cytoplasmic combinations of sorghum has been examined. Cytoplasmic genotypes were classified into eleven groups on the basis of restriction endonuclease digestion of mitochondrial DNA (mtDNA) and five groups on the basis of mitochondrial translation products. These cytoplasms were further characterized by hybridization of specific gene probes to Southern blots of EcoRI digested mtDNA, and identification of the fragment location of four mitochondrial genes. Variation was observed in the genomic location and copy number of the F1 ATPase α-subunit gene, as well as the genomic location and gene product of the cytochrome c oxidase subunit I gene. The effect of nuclear genotype on mitochondrial genome organization, expression and the presence of two linear plasmid-like mtDNA molecules was examined. Our results indicate that nuclear-mitochondrial interactions are required for regulation of mitochondrial gene expression. When a cytoplasm is transferred from its natural to a foreign nuclear background some changes in the products of in organello mitochondrial protein synthesis occur. In a number of cytoplasmic genotypes these changes correlate with the expression of cytoplasmic male sterile phenotype, suggesting a possible molecular basis for this mutation.

A comparison between mitochondrial DNA of an isogenic male-sterile (5) and male-fertile (F) couple (HA89) of sunflower

Mitochondrial DNA from etiolated seedling of male-fertile (F) and male-sterile (S) sunflower (Helianthus annuus L.) has been investigated for the first time in an isogenic couple HA89. 1. The mt-DNAs isolated from the S and F cytoplasms give a sharp and symmetrical band at 1.706 g/ml in an analytical CsCI gradient ultracentrifugation. 2. In polyacrylamide gel it is found that mitochondria from F cytoplasm contain a Low-Molecular-Weight (LMW) mt-DNA molecule of 1.45 Kilobase-pairs (kb) in addition to the major mt-DNA. On the contrary, mitochondria from S cytoplasm contain no LMW molecule. Treatments with DNAse, RNAse and Nuclease S1 show that this LMW mt-DNA molecule consists of a supercoiled circular DNA. The length and form of the LMW molecule are confirmed by electron microscopy observations. 3. The mt-DNAs from S and F cytoplasms have also been investigated using restriction endonuclease digestions (Sa11, Xho1, Bg11). The electrophoresis of the resulting fragments reveals several differences between the S and F cytoplasm. It is not known whether the differences observed between F and S mt-DNA are correlated with the cytoplasmic male sterility phenotype.

Identification and characterization of double-stranded RNA associated with cytoplasmic male sterility in Vicia faba

The cytoplasmic male sterility (CMS) trait of at least one line of Vicia faba plants is always associated with the presence of high molecular weight double-stranded RNA in the leaf tissue extracts. Subcellular fractions of leaf tissue from CMS and fertile maintainer plants were initially analyzed in an attempt to locate, identify, and characterize the genetic material involved with the sterility trait. This CMS-associated high molecular weight RNA was found only in the cytosol of the "447" male sterile line of V.faba plants and could not be isolated from the recurrent parent (maintainer), from lines that had been fertility-restored, or from lines that had reverted from the sterile condition. We have been able to move the CMS-associated RNA from donor to fertile host plants through a dodder bridge. These hots not only contain the RNA but now exhibit a male sterile phenotype, as detected by visual examination of the flower, the pollen, morphological characteristics, and pollen staining ability.

Organogenesis from cultured floral meristems of a male sterile tobacco hybrid

Very young floral meristems of a male-sterile tobacco hybrid were excised and cultured on Linsmaier and Skoog medium in continuous light. Basal medium was supplemented with kinetin and gibberellic acid, singly and in combinations. On medium with kinetin, all four types of floral organs arose in the normal sequence and pattern and the male sterile phenotype was expressed, GA3 suppressed the formation of these organs. The data show that male sterile organs may form and begin differentiation in vitro without direct influence from the plant.

Genic Male Sterility in the Common Bean (Phaseolus vulgaris L.)1

Abstract A male sterile bean plant was observed in the F2 population of WI 74-2047 × ‘Swedish Brown’. Male sterile phenotypes were characterized by all pollen grains being shriveled and non-functional, but with female fertility unaffected. Expression of sterility was genic, involving 2 unlinked loci, Ms1 and In-ms1, which interact to give a 13:2:1 F2 ratio of non-sterile:sterile:lethal individuals. ‘Swedish Brown’ contained fully fertile and semisterile plants, the latter presumed to be caused by the presence of a reciprocal translocation. One of the loci involved in male sterility is loosely linked to one of the break points of the translocation, and lines segregating for sterility but not semisterility were obtained.

Nuclear and cytoplasmic genes controlling synthesis of variant mitochondrial polypeptides in male-sterile maize

The polypeptides synthesized in vitro by mitochondria isolated from etiolated maize shoots of a number of different nuclear and cytoplasmic genotypes have been compared by using polyacrylamide gel electrophoresis. We have previously shown that mitochondria from maize plants carrying the T or C forms of cytoplasmically inherited male sterility (cms-T and cms-C mitochondria) can be distinguished from each other and from the mitochondria of normal (N) plants by the synthesis of a single additional or variant polypeptide species. Using lines that carry the T cytoplasm, and that differ principally in the presence or absence of nuclear "restorer" alleles that suppress the male-sterile phenotype, we find that these nuclear genes specifically suppress synthesis of the 13,000 M(r) variant polypeptide. A 21,000 M(r) polypeptide that is synthesized by N mitochondria is not detectable among the translation products of cms-T mitochondria from either restored or nonrestored lines. Results obtained with a number of lines possessing dominant restorer alleles from different sources indicate that it is the restorer gene at the Rf(1) locus that is primarily responsible for regulating synthesis of the 13,000 M(r) polypeptide. Mitochondria from lines with the S form of cytoplasmic male sterility (cms-S) were found to synthesize a group of minor polypeptides, ranging in molecular weight from 42,000 to 88,000, which were not detected in N, cms-T, or cms-C mitochondria. In the case of the S and C forms of male sterility no differences were found between the translation products of mitochondria from restored and nonrestored lines.

A male sterile pepper (C. annuum L.) mutant

1. After treatment of dry seeds of red pepperCapsicum annuum L. with X-rays a male-sterile mutant was discovered in the M2. 2. The male-sterile mutant segregates in a ratio of 3.28:1 (χ(2)=3.148, probability 0.07). 3. After an alternative cultivation of male-sterile plants and of a variety with good combining ability relatively good fruit-setting and seed production was obtained. 4. Grafting of male-sterile scions to normal stocks does not affect the male-sterile phenotype.