* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download supplementary materials
Biology and sexual orientation wikipedia , lookup
Population genetics wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Saethre–Chotzen syndrome wikipedia , lookup
Point mutation wikipedia , lookup
Medical genetics wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Designer baby wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Gene expression programming wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Segmental Duplication on the Human Y Chromosome wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Genomic imprinting wikipedia , lookup
Microevolution wikipedia , lookup
Genetically modified organism containment and escape wikipedia , lookup
Dominance (genetics) wikipedia , lookup
Genome (book) wikipedia , lookup
Skewed X-inactivation wikipedia , lookup
Y chromosome wikipedia , lookup
SUPPLEMENTARY MATERIALS Selection of the A-A translocation and markers Construction of new B-A-A translocations and successful screening for them requires that two conditions be met. First, it is necessary to select an A-A translocation wherein one of the chromosome arms involved in the interchange is the same arm as that borne on the simple B-A chromosome and that the breakpoint in the arm of shared homology of the A-A translocation be distal to the breakpoint of the A chromosome arm borne on the B-A. The greater the distance between these two breakpoints, the greater the extent of shared homologous region of that arm and the greater the likelihood of synapsis and crossing over within that region resulting in a recombinant B-A-A chromosome. Second, the breakpoint in the A chromosome arm of the distal-most segment of the B-AA translocation has to be proximal to the location of the marker locus in the tester stock used to screen for the new B-A-A translocation. This assures that the distal-most segment can bear the dominant allele of the marker locus and that the endosperm marker phenotype can be uncovered in the hypoploid endosperm. Selection of suitable B-A/A-A plants for pollen to cross onto tester stocks Consideration must be given to whether or not a potential pollen parent plant carries the simple B-A chromosome, and also whether or not it carries the A-A translocation chromosomes. Because the B-A stock plants used as female parents of the initial cross are grown from kernels containing embryos that are hyperploid for the B-A chromosome (two copies of the B-A chromosome) most of these plants will carry the BA chromosome. The A-A stocks used as pollen parents of the initial cross are grown from kernels containing embryos that are either homozygous (T/T) or are heterozygous 39 (N/T) for the A-A translocation. In the former case all progeny plants grown from kernels produced by the initial cross will carry the A-A translocation and will be heterozygous for it (N/T). But in the latter case, where the pollen parent used to make the initial cross is N/T then half of the progeny plants will carry the A-A translocation and be heterozygous for it (N/T) and half will not carry the translocation (N/N). In either case, it is important to verify that the progeny plants which are to be used to cross onto testers carry the A-A translocation. Verification of the presence of an A-A translocation or an inversion in a maize stock can readily be accomplished by examination of the pollen of candidate plants. This is easily done by using a pocket microscope to score pollen sprinkled onto a black bottle cap from a freshly extruded anther whose tip has been pinched off (DOYLE 1993). Because plants heterozygous for an A-A translocation produce microspores that are duplicate-deficient for chromosome segments and microspores with a complete balanced set of chromosomes in a 1:1 ratio, plants that are heterozygous for an A-A translocation (N/T) can be readily identified by their approximately 50% pollen abortion frequency. Whereas normal pollen grains are opaque and appear like white pearls, aborted pollen grains appear empty, translucent, collapsed, or otherwise grossly abnormal (DOYLE 1993). The B-A/A-A pollen parent plants need to carry both the B-A and the A-B chromosomes The sources of pollen parents to be crossed onto appropriate kernel trait tester stocks are plants grown from kernels produced by crossing plants containing A-A translocations onto plants carrying simple B-A translocations. The latter plants are hyperploid for the B-A and contain two B-A chromosomes and one corresponding A-B 40 chromosome. The plants containing A-A translocations are identified by pollen semisterility, and therefore are heterozygous for the translocated chromosomes. Consequently, among the progeny of the cross of the B-A stock by the A-A stock most will contain the simple B-A chromosome and approximately half of them will also carry the A-B chromosome. Furthermore, among these same progeny, approximately half of the plants will carry the A-A translocation, and these will be heterozygous for the translocation and can be identified by their pollen semisterility. In most cases this semisterility approaches 50% but in those instances where one or both of the translocation breakpoints are located in the distal region of the chromosome arms the percent of aborted pollen may approach 25% (See BURNHAM 1978 for a detailed discussion). In most cases, the identification of plants carrying an A-A translocation is not difficult, and approximately half the plants in a 20 kernel family planted as a sourse of B-A/A-A pollen parents will be identified as carrying the A-A translocation by their pollen semi-sterility. In addition to carrying the A-A translocation, the pollen parents need to carry both the simple B-A chromosome and the A-B chromosome in order to be suitable for creating B-A-A stocks carrying the A-B chromosome. The compound B-A-A stocks need to carry the A-B chromosome in order to be euploid and for the B-A-A to regularly undergo nondisjunction during the second pollen mitosis which results in the production of the hyperploid and hypoploid sperm. Selection of testers for screening for new B-A-A translocations The most useful tester stocks for crossing onto with pollen from B-A/A-A heterozygotes are stocks carrying either in the homogyzous or heterozygous condition a 41 recessive allele for one of the eight aleurone color factors, while all of the other of the factors are present in the homozygous dominant condition. These color factors, their recessive aleurone phenotypes, and their chromosome arm locations are bz2, bronze, 1L; a1, colorless, 3L; c2, colorless, 4L; a2, colorless, 5S; pr1 red, 5L; c1, colorless, 9S; bz1, bronze, 9S; and r1, colorless, 10L. These tester stocks are conveniently used in combination with the presence of a dominant R1 allele such as R1-scm 2 that conditions the scutellum region of the embryo to have a purple color when all of the color factors are represented in the embryo by at least one dose of their dominant allele (ROBERTSON 1967). These are the kinds of stocks most widely used in creating the new B-A-A translocations reported here. For example, a c2 tester used to screen for new B-A-A recombination events where the distal A chromosome segment of the new B-A-A will be a distal portion of chromosome arm 4L, will have a genotype of Bz2/Bz2, A1/A1, c2/c2, A2/A2, Pr1/Pr1, C1/C1, Bz1/Bz1, and R1-scm2/R1-scm2. Pure breeding purple kernel stocks produce ears, when self pollinated, whereon all of the kernels have a purple aleurone comprising the outermost layer of the endosperm. If they are homozygous for the R1-scm2 allele, all of their embryos will be purple colored. Most of the colorless endosperm inbred stocks (with yellow or white kernels) used for hybrid corn seed production, and also used to propagate cytogenetic stocks such as the A-A translocation stock collection, are homozygous recessive for both the c1 locus on 9S and the r1 locus on 10L. This is a complicating factor when aiming to create new B-A-A translocations involving distal regions of chromosome arms 9S or 10L. This is because commonly the A-A translocation stock that is crossed onto a simple B-A stock to make a B-A/A-A heterozygote is c1/c1, r1/r1 and thus the B-A/A-A stock will carry both 42 the c1 and r1 recessive alleles. Consequently when the B-A/A-A stock’s pollen is crossed onto a 9S (c1/c1) or 10L (r1/r1) tester; one-half or more of the resulting kernels may be colorless, i.e. c1/c1 or r1/r1. This may be avoided by converting A-A translocations into pure breeding purple kernel stocks and employing simple B-A stocks that are homozygous for the dominant C1 and R1 alleles. The aleurone color stocks are limited in their usefulness because the aleurone color loci are not located at the ends of the chromosome arms bearing them. They are only useful when screening for new B-A-A stocks where the distal A segment of the new B-A-A includes the gene locus for the aleurone color factor borne on that arm of interest. Ordinarily, the dominant color condition allele is present for that locus in the A-A stock used to make the B-A/A-A heterozygous (except for c1 and r1, as noted above). When this is the case then the new B-A-A chromosome will carry in its distal A segment the dominant allele of the tester stock locus. This means that the hyperploid sperm containing two copies of the new B-A-A will provide the dominant color factor so that the hyperploid tissue product of double fertilization will be purple colored while the hypoploid product of fertilization will lack anthocyanin and be colorless (white or yellow). All kernel tester traits are limited in their use by the general rule that they are useful for detecting new B-A-A translocations only when the breakpoint of the A chromosome arm of interest (in the A-A chromosome translocation stock) is proximal to the location of the tester gene locus on that arm. In the example described above of the production of the new B-A-A TB-1Sb-4L 002-19 1S.87 4L.42, the new B-A-A event was discovered as a colorless endosperm/colored embryo kernel. This was possible because 43 the c2 locus on chromosome arm 4L is distal to the breakpoint at the cytological position of 0.42 on 4L and therefore the dominant C2 allele is borne on the distal 4L segment of the B-A-A chromosome. The egg cell of the tester stock contained a recessive c2 allele but the hyperploid sperm containing two doses of the C2 bearing B-A-A chromosome fertilized the egg to produce an embryo that was C2/C2/c2 and therefore colored. The hypoploid recessive c2 polar nuclei were fertilized by the hypoploid sperm nucleus lacking any allele at the c2 locus and therefore the resulting endosperm was colorless because it lacked the dominant C2 allele that is required for anthocyanin synthesis. There are two additional classes of kernel trait markers that are useful in screening for new B-A-A translocations. First are the genes that in the mutant recessive allelic state block or reduce carotenoid synthesis resulting in white or lemon-yellow colored kernels instead of the full yellow kernel normally exhibited by kernels carrying one or more doses of the dominant Y1 allele. These include some of the genes with mutant viviparous phenotypes. Particularly useful have been vp5 on chromosome arm 1S in our study, and w3 on chromosome arm 2L (RAKHA and ROBERTSON 1970). Additional markers with reduced yellow pigmentation include al1 on 2S, cl1 on 3S, lw1 on 1L, lw2 on 5L, vp1 on 3L, y10 on 3L, vp9 on 7S and y9 on 10S (See BECKETT 1991 for further descriptions including seedling factors for confirming the presence of a B-A or B-A-A chromosome). All of the above noted mutant loci result in an albino or light colored seedlings except for y9. The latter shows a normal seedling phenotype in our nurseries, but in some environments it produces pale green seedlings. Two additional loci are useful as markers and both are embryo or seedling lethals. These are the anl1 locus on chromosome arm 5S which results in a light colored or gray endosperm and an 44 unviable embryo, and the w2 locus on chromosome arm 10L which results in a mutant kernels in a purple kernel stock displaying a mottled purple aleurone phenotype, and producing albino seedlings. Both anl1 and w2 are distal to the more commonly used a2 and r1 loci on chromosome arms 5S and 10L, respectively, and are therefore useful for detecting new B-A-A translocations involving breakpoints distal to the a2 and r1 loci. Second are the numerous genes represented by the defective kernel (dek) mutations that have been found to be located thoughout all of the chromosome arms except for 8S (NEUFFER et al. 1986; NEUFFER and SHERIDAN 1980; SCANLON et al. 1994). These mutations affect to varying degrees both endosperm and embryo development. For many of the mutations, embryo development is so seriously impaired that the embryos or resulting seedlings suffer lethality (SHERIDAN and NEUFFER 1980, 1981). These lethal types of dek mutations are especially useful when they are used as tester stocks because any contaminating self pollinated kernels or mutant phenotype kernels that are produced by previously unknown allelism of testers will fail to produce normal plants. Some of the dek mutations, especially those resulting in a collapsed endosperm phenotype, result in such a severely reduced endosperm that kernels with mutant (hypoploid) endosperm and normal (hyperploid) embryos may require germination and initial culturing in the greenhouse. Dosage and deficiency analyses using B-A-A stocks Simple B-A chromosome stocks can be used as pollen parents to produce kernels with endosperms that are hypoploid (2X) or hyperploid (4X) for the A chromosome segment borne on the B-A chromosome [which is the segment distal to the breakpoint in the A chromosome; i.e., 0.05 to 1.00 (the end) of 1S in TB-1Sb], and with embryos that 45 are hypoploid (1x) or hyperploid (3x) for that A segment. The possibilities are more complex when using B-A-A stocks as pollen parents in making crosses. Such crosses produce kernels with endosperms that are hypoploid (2X) or hyperploid (4X) for the two A chromosome segments borne on the B-A-A chromosome (TB-1Sb-4L 002-19) [with the 1S segment from 0.05 to 0.87 and the 4L segment from 0.42 to 1.00 comprising the A-A region of the B-A-A chromosome], and whose embryos are, respectively, hyperploid (3X) or hypoploid (1X) for these chromosome segments. This results in the B-A-A pollen parent contributing either a duplicate or deficient segment for a chromosome region of two different A chromosomes. Furthermore, although a compound B-A-A chromosome stock can produce progeny with hyperploid and hypoploid tissues for both A chromosome segments, the first segment (attached to the B chromosome) is always an interstitial region of an A chromosome while the second segment (the distal-most of the A segments of the B-A-A) is always a distal region extending to the end of the chromosome arm of the A chromosome. Therefore tissues (endosperm or embryo) that are hyperploid or hypoploid for the B-A-A chromosome will be either duplicate (with an extra copy) or deficient (lacking a copy) for an interstitial region of one A chromosome arm and for a distal region of another A chromosome arm. These features of hyperploid and hypoploid doses and their consequences for duplication and deficiency of chromosome regions are shown in Supplementary Materials Figure 2. 46 REFERENCES FOR SUPPLEMENTARY MATERIALS BECKETT, J. B., 1993 Locating recessive genes to chromosome arm with B-A translocations, pp. 315-327 in The Maize Handbook, edited by M. FREELING and V. WALBOT, Springer-Verlag, New York. BURNHAM, C.R. 1978 Cytogenetics of interchanges, pp. 673-692 in Maize Breeding and Genetics, edited by D.B. Walden. John Wiley and Sons, New York. DOYLE, G.G., 1993 Inversions and list of inversions available, pp 346-349 in The Maize Handbook, edited by M. FREELING and V. WALBOT. Springer-Verlag, New York. NEUFFER, M. G. and W .F. SHERIDAN, 1980 Defective kernel mutants of maize I. Genetic and lethality studies. Genetics 95: 929-944. NEUFFER, M. G., M. T. CHANG, J. K. CLARK, W. F. SHERIDAN, 1986 The genetic control of maize kernel development, pp. 35-50 in Regulation of Carbon and Nitrogen Reduction and Utilization in Maize, edited by J. C. SHANNON, D. P. KNIEVEL, and C. D. BOYERS. Am Soc Plant Physiol, Rockville, MD. RAKHA, F. A. and D. S. ROBERTSON, 1970 A new technique for the production of AB translocations and their use in genetic analysis. Genetics 65: 223-240. ROBERTSON, D. S., 1967 The use of R2scm to facilitate the transfer of maize chromosomal segments. J. Heredity 58:152-156. SCANLON, M. .J., P. S. STINARD, M. G. JAMES, A. M. MYERS, D. S. ROBERTSON, 1994 Genetic analysis of 63 mutations affecting maize kernel development isolated from Mutator stocks. Genetics 136: 281-294. SHERIDAN, W. F.and M. G. NEUFFER, 1980 Defective kernel mutants of maize. II. Morphological and embryo culture studies. Genetics 32: 945-960. 47 SHERIDAN, W. F. and M. G. NEUFFER, 1981 Maize mutants altered in embryo development, pp. 137-156, in Levels of Genetic Control in Development, edited by S. SUBTELNEY and U. ABBOTT. New York. 48 Supplementary Materials Figure Legends Figure 1. – When fertilization of egg and polar nuclei of a c2 tester plant (A) is accomplished by sperm of a pollen grain carrying normal chromosomes and the recessive c2 allele (B), then a concordant kernel results with both the embryo and the endosperm being colorless (C). Figure 2.– When an embryo sac containing a normal chromosome 1 and a normal chromosome 4 (bearing the recessive c2 allele) receives a hyperploid and a hypoploid sperm from a pollen grain carrying a B-1-4 and 1-B chromosome and 4-1 translocated chromosome, the dosage of chromosome segments and genetic markers in the endosperm and embryo resulting from fertilization by the hyperploid and hypoploid sperm will vary, depending on which of the two sperm fertilizes the egg and which fertilizes the polar nuclei. (A) In the case of the polar nuclei fusing with the hyperploid sperm the resulting endosperm will be hyperploid for the region on 1S from 0.05 distal to 0.87 and hyperploid for the region on 4L from 0.42 distal to 1.00 (the end of the chromosome). However, the distal most regions of chromosome arms 1S and 4L will differ in dosage; for 1S, the region from 0.87 distal to 1.00 will be 3X in dosage while for 4L, the region from 0.42 distal to 1.00 will be 4X in dosage. (B) The reciprocal dosage ratios will occur in the endosperm resulting from fusion of the hypoploid sperm with the polar nuclei. Here the endosperm will be hypoploid for the 1S region from .05 distal to 0.87 and hypoploid for the 4L region from 0.42 distal to 1.00. However, the distal most regions of chromosomes arms 1S and 4L will differ in dosage because the 1S region from 0.87 distal to 1.00 will be 3X in dosage (as in the endosperm shown in A), but the 4L region from 0.42 distal to 1.00 will be 2X in dosage. (C) When the hyperploid sperm 49 fertilizes the egg, the resulting embryo will be hyperploid for the 1S region from 0.05 distal to 0.87 and hyperploid for the 4L region from 0.42 distal to 1.00. But, as in the case for the endosperm, the distal most regions of chromosome arms 1S and 4L will differ; for 1S, the region from 0.87 distal to 1.00 will be 2X in dosage, while for 4L, the region from 0.42 distal to 1.00 will be 3X in dosage. (D) The reciprocal dosage ratios will occur in the embryo resulting when the hypoploid sperm fertilizes the egg. This embryo will be hypoploid for the 1S region from 0.05 distal to 0.87 and hypoploid for the 4L region from 0.42 distal to 1.00. But the distal most regions of chromosome arms 1S and 4L will differ; for 1S the region from 0.87 distal to 1.00 will be 2X in dosage, while for 4L, the region from 0.42 distal to 1.00 will be 1X in dosage. 50