This is the oldest English language journal in genetics. Founded by W. Bateson and R. C. Punnett in 1910, the Journal of Genetics was later edited by J. B. S. Haldane; later, Haldane and his wife, Helen Spurway brought the journal with them to India. After his death in 1964, Mrs. Haldane continued publication of the journal, with Madhav Gadgil and H. Sharat Chandra (Indian Institute of Science, Bangalore) and Suresh Jayakar (Laboratorio de Genetica Biochimica ed Evoluzionistica, Pavia) as editors, until her own death in 1977. In 1985, with the permission of Haldane’s heirs, the Indian Academy of Sciences resumed publication of the journal. The journal retains its traditional interest in evolutionary research that is of relevance to geneticists, even if not explicitly genetic in nature.

The journal of genetics

Sex chromosomes evolved from autosomes many times across the eukaryote phylogeny. Several models have been proposed to explain this transition, some involving male and female sterility mutations linked in a region of suppressed recombination between X and Y (or Z/W, U/V) chromosomes. Comparative and experimental analysis of a reference genome assembly for a double haploid YY male garden asparagus (Asparagus officinalis L.) individual implicates separate but linked genes as responsible for sex determination. Dioecy has evolved recently within Asparagus and sex chromosomes are cytogenetically identical with the Y, harboring a megabase segment that is missing from the X. We show that deletion of this entire region results in a male-to-female conversion, whereas loss of a single suppressor of female development drives male-to-hermaphrodite conversion. A single copy anther-specific gene with a male sterile Arabidopsis knockout phenotype is also in the Y-specific region, supporting a two-gene model for sex chromosome evolution.

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The asparagus genome sheds light on the origin and evolution of a young y chromosome

Plant population biology: edited by A.J. Davy, M.J. Hutchings and A.R. Watkinson, Blackwell Scientific Publications (28th Symposium of the British Ecological Society), 1988. £40.00 hbk (viii + 478 pages) ISBN 0 632 02349 X

Dioecy, the presence of male and female flowers on separate individuals, is both widespread and uncommon within flowering plants, with only a few percent of dioecious species spread across most major phylogenetic taxa. It is therefore safe to assume that dioecy evolved independently in these different groups, which allows us to ask questions regarding the molecular and developmental mechanisms underlying these independent transitions to dioecy. We start this review by examining the problem from the standpoint of a genetic engineer trying to develop dioecy, discuss various potential solutions, and compare them to models proposed in the past and based on genetic and evolutionary considerations. Next, we present recent information regarding candidate sex determinants in three species, acquired using newly established genomic approaches. Although such specific information is still scarce, it is slowly becoming apparent that various genes or pathways can be altered to evolve dioecy.

One Hundred Ways to Invent the Sexes: Theoretical and Observed Paths to Dioecy in Plants.

Lycoris longituba is one of the species belonging to the Amaryllidaceae family. Despite its limited distribution, endemic to central eastern China, this species displays an exceptionally wide diversity of flower colors from purple, red, orange, to yellow, in nature. We study the natural variation of floral color in L. longituba by testing the components of water-soluble vacuolar pigments – anthocyanins – in its petals using high-performance liquid chromatography coupled with photodiode array detection and electrospray ionization mass spectrometry. Four anthocyanins were identified, cyanidin-3-sophoroside (Cy3So), cyanidin-3-xylosylglucoside (Cy3XyGlc), cyanidin-3-sambubioside (Cy3Sa), and pelargonidin-3-xylosylglucoside (Pg3XyGlc), which occur at various amounts in L. longituba petals of different colors. A multivariate analysis was used to explore the relationship between pigments and flower color. Anthocyanins have been thought to play a major role in acting as a UV screen that protects the plant's DNA from sunlight damage and attracting insects for the purpose of pollination. Thus, knowledge about the content and type of anthocyanins determining the petal coloration of Lycoris longituba will help to study the adaptive evolution of flowers and provide useful information for the ornamental breeding of this species.

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0022098&type=printable

Natural Variation in Petal Color in Lycoris longituba Revealed by Anthocyanin Components

Garden asparagus (Asparagus officinalis L.) is an economically important plant with 2n = 2x = 20 chromosomes and a haploid genome size of 1323 Mb (Bennett and Leitch 2003). The karyotype of asparagus consists of five long (L), one medium (M) and four small (S) chromosomes (Löptien 1976). Plants of this dioecious species differ in producing either male or female flowers. The sexual dimorphism in asparagus is controlled by a region located on a pair of homomorphic sex chromosomes (chromosome L5) (Löptien 1979) termed the M locus (Flory 1932; Uno et al. 2002). Maleness is dominant with males normally heterogametic (Mm) and females homogametic (mm). Supermales (MM) can be produced from anther culture or from rarely occurring andromonoecious plants. The identification of chromosome L5 is important for studying sex chromosome evolution in asparagus. However, it was observed that the sex chromosome pair is homomorphic: X and Y chromosomes do not differ in morphology. Telgmann-Rauber et al. (2007) tried to clone the region determining sex in asparagus from its position in the genome. Molecular cytogenetic and sequence analyses of bacterial artificial chromosomes (BACs) flanking M locus indicate that the BAC contain highly repetitive sequences that localize to centromeric and pericentromeric locations on all asparagus chromosomes. However, the L5 chromosome could not be distinguished by BAC-FISH (Telgmann-Rauber et al. 2007). Recently, FISH has become a powerful and useful tool for the direct detection of specific DNA in genome. In this technique, ribosomal DNA genes (45S and 5S rDNA) are commonly used as markers for the physical mapping of plant chromosomes to analyse genomic organization (Nakayama et al. 2001; Lan et al. 2006; Grabowska-Joachimiak et al.

Karyotype of asparagus by physical mapping of 45S and 5S rDNA by FISH.

Lycoris longituba Y. Hsu et Q. J. Fan is a perennial, bulbiferous, herbaceous plant of the family Amaryllidaceae. It is endemic in China, with a very limited distribution, being found only at Langyashan in Anhui province, and Baohuashan and Xuyi city in Jiangsu province, all located about 50 km from one another (see figure 1 and table 1 in electronic supplementary material at http://www.ias.ac.in/jgenet/). A unique biological characteristic of this plant is that its leaves come out in spring and die in early summer, followed by flowering. Thus, its vegetative growth and reproduction are discrete, which is rare in angiosperms. With a vigorous and long scape, its flowers are diverse in both colour and floral form, and fragrant in smell, and have high ornamental value. Also called Chinese tulip, this species is ideal for ikebana, and its bulb has medicinal properties. We have collected more than 70 variants of this species in our laboratory with different floral colours and forms. Population-genetic structure is considered as spatiotemporal distribution of genetic variation (Ge 1997), and reflects evolutionary processes in populations (Hamrick and Loveless 1989). To take right measures to protect wild resources of L. longituba, it is important to study the range of genetic variation, genetic structure, diversification trend and other factors affecting genetic structure of the populations of this important and sparsely distributed species. Presently, many biochemical and DNA-based markers are used in studies of population structure. The random amplified polymorphic DNA (RAPD) method (Williams et al. 1990) is frequently applied to reveal population-genetic variation, divergence and biogeography (Schaal and Leverich 2001). A large number of studies have successfully applied this method to study genetic variation in plants owing to

Assessment of genetic diversity of Lycoris longituba (Amaryllidaceae) detected by RAPDs.

Ion implantation, a new biophysically mutagenic technique, has shown great potential for crop breeding. To reveal the mutation effect of low-energy ion implantation on Baiyangdian red lotus, sequence-related amplified polymorphism markers were used to amplify and detect the DNA sequence differences in mutants induced by Fe(+) ion implantation. A total of 121 primer combinations were tested in 6 mutants and a control. Seven primer combinations (me1 + em3, me1 + em14, me9 + em3, me8 + em2, me6 + em1, me11 + em5, and me6 + em5) generated clear bands with high polymorphism and good repeatability. The results showed that among 15,317 bases cloned, 146 bases in 6 mutants were different from those of the wild type, showing a variation frequency of 0.95%. The types of base changes included deletion, insertion, transversion, and transition. Adenine was more sensitive to the irradiation than were the other bases. The results suggested that mutational "hotspots" probably exists in lotus and are induced by low-energy ion implantation.

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SRAP analysis of DNA base sequence changes in lotus mutants induced by Fe⁺ implantation.

Multiple-PCR was conducted to establish a stable PCR system for identifying the three Wx genes in wheat. Two pairs of primers were employed to amplify Wx-A1, Wx-B1, and Wx-D1 genes of wheat, with the target sequences of 230 bp/265 bp, 854 bp, and 204 bp, respectively. The results showed that Wx-A1, Wx-B1, and Wx-D1 can be detected simultaneously in a single reaction. This method proved to be repeatable and low cost for evaluation of wheat quality properties in breeding program. This multiple-PCR technique can be efficiently used in marker-assisted selection for Wx genes, which will improve selection procedure for waxy wheat.

[Molecular identification on Waxy genes in wheat using multiple-PCR].

Ion implantation, as a new biophysically mutagenic technique, has shown a great potential for horticultural plant breeding. Up to date, little is known about the mutation mechanism of ion implantation at the DNA level. To reveal the mutation effect of Fe+ ion implantation on Baiyangdian red lotus, the random amplified polymorphic DNA (RAPD) was used, and then the bands of mutants and the control in the radiation-sensitive sites were cloned to be sequenced for comparing their DNA sequences. The results indicated that the total base mutation rate of mutants was 0.87%, and there was different in the six mutants. The types of base changes included base transition, transversion, deletion, and insertion. Among the 159 base changes detected, the frequency of single base substitutions (61.01%) was higher than that of base deletions and insertions (38.99%), and the frequency of base transitions (44.65%) was 2.7 times of that of the base transversions (16.35%). The transitions between C and T accounted for largest proportion, A→G transitions and A→T transversions were also present at high frequency. Adenine, thymine, guanine or cytosine could be replaced by any of other three bases, except that there was no C → G substitution. However, thymine was more sensitive to the irradiation than other bases. In our study, we found many purine bases around the purine mutational sites, and many pyrimidine bases around the pyrimidine mutational sites. These will further help us to understand the mechanism of mutagenesis by ion implantation.

Chuan-Liang Deng

Papers

Karyotype of asparagus by physical mapping of 45S and 5S rDNA by FISH.

Assessment of genetic diversity of Lycoris longituba (Amaryllidaceae) detected by RAPDs.

SRAP analysis of DNA base sequence changes in lotus mutants induced by Fe⁺ implantation.

[Molecular identification on Waxy genes in wheat using multiple-PCR].

Preliminary study on molecular mechanism of lotus mutants induced by ion implantation