Evolution of plant reproduction: from fusion and dispersal to interaction and communication

Based on the existing data concerning the evolution of the sexual reproduction, it is argued that the processes of sex differentiation and interactions play a key role in evolution. From the beginning environment and organism are unified. In a changing dynamic environment life originates and the interaction between life and environment develops from simple to more complex organisms. Sexual reproduction is introduced after the origin of meiosis and is a key process in evolution. The asexual reproduction process prepares to dispersal. Sexual reproduction process adds the genome renewal and the gamete-gamete interaction. Reproduction and dispersal are connected and the process of reproduction has similarities between asexual and sexual reproduction. Unicellular algae develop the physiological and morphological sex differentiation. Sex differentiation is connected with the way of dispersal. The step to multicellular plants introduces cell isolation after meiosis and by the stay on the mother plant within a cell or organ, plant-cell apoplastic interaction originates and by prolonged stay the plant-plant interaction. This stay influences the type of dispersal. A life cycle with alternation of generations and two moments of dispersal permits plants to go on land. In ferns a shift in the moment of sex differentiation to meiospore happens and the stay of the macrospore leads to the seed plants. In water all types of sexual reproduction, interactions and the alternation of generations are prepared and these are used to conquest land. On land the biotic dispersal is realized. The phylogeny of sexual reproduction reveals that the sex differentiation and interaction are the main causes in the evolution of sexual reproduction. Sexual reproduction shows interactions during gamete fusion, between organism and environment and in multicellular plants between organisms. With respect to other types of interaction as in symbiosis or the nutrient chain, interaction is considered as an important action which is based on a persisting cooperation and points to a push during evolution. The push is expressed as communication: the driving force in the evolution. Based on the interactions between organisms and interactions between organisms and the dynamic environment, communication is considered as a driving force leading to the evolution as explained in the development of plant reproduction. Consequences for reproduction, its regulation and the process of evolution are discusse

Sexual reproduction in Phytophthora infestans

Potato late blight, caused by the oomycete Phytophthora infestans, is one of the most devastating plant diseases worldwide. It is becoming increasingly difficult to control the disease in Sweden, leading to an ever more intensified use of fungicides in the potato production. This unsustainable development could be caused by changes in the pathogen due to the introduction of sexual reproduction. These changes could result in an enhanced capability of the pathogen to adapt to different factors, e. g. weather, cultivar resistance, chemical control or other cultivation measures. This might manifest itself in earlier infections and a late blight that spreads faster in the potato fields requiring increasing efforts to control. Different approaches were taken to clarify the role of sexual reproduction in P. infestans in the epidemiology of potato late blight. The formation of sexually formed oospores and their ability to serve as primary inoculum was studied, both as field observations and by determining within-field genotypic diversity. To further estimate the importance of reproduction on a large spatial scale a population study based on molecular and phenotypic markers was performed on P. infestans isolates from the whole Nordic region. The variation in the aggressiveness of Nordic populations of P. infestans was studied by determining different components of aggressiveness, e.g. sporulation capacity, lesion growth and infection efficacy. The aggressiveness study was combined with an analysis of the phenotypic structure of the Nordic population of P. infestans. The results clearly indicate that the Swedish populations of P. infestans are influenced by sexual reproduction. The facts that both mating types are found all over the country in near 1:1 proportions and that oospores are commonly formed in field crops and serve as inoculum under field conditions support this. Studies of the genetic diversity also indicate that sexual reproduction has an effect on the population structure of P. infestans in Sweden and the Nordic region as a whole

Monte Carlo Simulations of Sexual Reproduction

Modifying the Redfield model of sexual reproduction and the Penna model of biological aging, we compare reproduction with and without recombination in age-structured populations. In contrast to Redfield and in agreement with Bernardes we find sexual reproduction to be preferred to asexual one. In particular, the presence of old but still reproducing males helps the survival of younger females beyond their reproductive age.Comment: 8 pages, plain tex, 7 EPS figures, to appear in PHYSICA

Biologically active Phytophthora mating hormone prepared by catalytic asymmetric total synthesis

A Phytophthora mating hormone with an array of 1,5-stereogenic centers has been synthesized by using our recently developed methodology of catalytic enantioselective conjugate addition of Grignard reagents. We applied this methodology in a diastereo- and enantioselective iterative route and obtained two of the 16 possible stereoisomers of Phytophthora hormone α1. These synthetic stereoisomers induced the formation of sexual spores (oospores) in A2 mating type strains of three heterothallic Phytophthora species, P. infestans, P. capsici, and P. nicotianae but not in A1 mating type strains. The response was concentration-dependent, and the oospores were viable. These results demonstrate that the biological activity of the synthetic hormone resembles that of the natural hormone α1. Mating hormones are essential components in the sexual life cycle of a variety of organisms. For plant pathogens like Phytophthora, sexual reproduction is important as a source of genetic variation. Moreover, the thick-walled oospores are the most durable propagules that can survive harsh environmental conditions. Sexual reproduction can thus greatly affect disease epidemics. The availability of synthetic compounds mimicking the activity of Phytophthora mating hormone will be instrumental for further unravelling sexual reproduction in this important group of plant pathogens.

Mate limitation, recurrent epidemic outbreaks, and the coexistence of sexual and asexual plant parasites

To date, relatively few studies have focused on the effects of sex on population dynamics. Previous models found that sexual reproduction may either dampen population fluctuations or accentuate population fluctuations, depending on mating system notably. Here we were interested in the effect of mate limitation in pathogens in which both sexual and asexual reproductions occur simultaneously within direct life cycles, a life history typical of many fungal plant pathogens for instance. We modelled the epidemiological dynamics of such species by considering a SIR model with two modes of transmission, one linear and the other bilinear in infected density. We found that the threshold for epidemic development is the same as expected under strictly asexual dynamics. We showed that sexual spore production promotes more complex dynamics (cycles) than strictly asexual reproduction. We further showed that sexual reproduction has important consequences for the coexistence of parasites infecting the same host: in parameter ranges where the parasite population dynamics fluctuate, the stable coexistence of parasites on the same host is possible, whereas it is not in the asexual case. We discuss the implications of these results for understanding complex epidemiological dynamics and point to some consequences for epidemics management. (Résumé d'auteur

HUBUNGAN ANTARA PENGETAHUAN KESEHATAN REPRODUKSI DAN KETAATAN BERAGAMA DENGAN SIKAP TERHADAP HUBUNGAN SEKS PRANIKAH (STUDI PADA SISWA KELAS II SMAN 1 SEMARANG) CORRELATION BETWEEN KNOWLEDGE OF REPRODUCTION HEALTH, RELIGIOUSNESS OBEDIENCE AND ATTITUDE TO PREMARITAL SEXUAL INTERCOURSE (STUDY ON THE SECOND GRADE STUDENTS OF SMAN 1 SEMARANG)

Kesehatan reproduksi remaja saat ini sudah menjadi isu global. Jumlah remaja yang besar dan secara seksual tergolong aktif, namun mempunyai pengetahuan kesehatan reproduksi yang relatif rendah sehingga kurang mendukung terciptanya remaja berkualitas. Selain itu aspek moral atau agama sangat diperlukan sebagai kontrol perilaku remaja khususnya yang berkaitan dengan hubungan seks pranikah. Tujuan penelitian ini untuk mengetahui hubungan pengetahuan kesehatan reproduksi dan ketaatan beragama dengan sikap terhadap hubungan seks pranikah. Penelitian ini bersifat explanatory research dengan pendekatan cross sectional. Sampel yang digunakan adalah siswa kelas II SMAN 1 Semarang sebanyak 79 orang yang diambil secara simple random sampling. Hasil penelitian diperoleh 68,4% responden berumur 16 tahun dan 83,5% memeluk agama islam. Tingkat pengetahuan kesehatan reproduksi responden 63,2% termasuk kategori cukup. Ketaatan beragama responden 78,5% termasuk kategori cukup. Sikap responden terhadap hubungan seks pranikah 51,8% termasuk kategori cukup. Hasil uji statistik dengan korelasi Rank Spearman antara variabel pengetahuan kesehatan reproduksi dengan variabel sikap terhadap hubungan seks pranikah diperoleh nilai r=0,425 dan p-value=0,000. Sedangkan untuk variabel ketaatan beragama dengan variabel sikap terhadap hubungan seks pranikah diperoleh nilai r=0,451 dan p-value=0,000. Secara statistik ada hubungan antara pengetahuan kesehatan reproduksi dan ketaatan beragama dengan sikap terhadap hubungan seks pranikah. Kesimpulan penelitian ini adalah ada hubungan antara pengetahuan kesehatan reproduksi dan ketaatan beragama dengan sikap terhadap hubungan seks pranikah. Disarankan kepada (1) pihak sekolah untuk memberikan informasi kesehatan reproduksi melalui pendekatan pengetahuan dan moral atau agama, (2) kepada BKKBN untuk membentuk kelompok remaja/siswa Peduli Kesehatan Reproduksi Remaja sebagai motivator dalam memasyarakatkan kesehatan reproduksi remaja di sekolah. Health of adolescent has become global issue this time. The great amount of adolescent and they pertained as sexually active, but relatively lack of knowledge about reproduction health so that less of supporting the creation of adolescent behavioral control specially related to premarital intercourse. The purpose of this research is to know the correlation between knowledge of reproduction health, religiousness obedience and attitude of premarital sexual intercourse. This research is explanatory research with approach of cross sectional study. Sample used in this research is 79 students of SMAN 1 Semarang at second grade taken by simple random sampling. Result of this research obtained by 68,4% responder`s are 16 years old anf 83,5% are moslem. The level of responder`s knowledge of reproduction health 63,2% are included to enough category. Responder`s religiousness obedience 78,5% are included to enough category. Responder`s attitude of premarital sexual intercourse 51,8% are included to enough category. Result of statistical test with correlation of Rank Spearman between knowledge of reproduction health variable and attitude of premarital sexual intercourse variable obtained value 0f r = 0,425 and p-value = 0,000. Meanwhile for the variable of religiousness obedience and attitude of premarital sexual intercourse variable obtained value of r = 0,451 and p-value =0,000. Statistically, there is correlation between knowledge of reproduction health and religiousness obedience and attitude of premarital sexual intercourse. The conclusion of this research is there is correlation between knowledge of reproduction health and religiousness obedience and attitude of premarital sexual intercourse. Suggested to (1) school party, that they need to give information about health reproduction through moral and knowledge or religion approach, (2) BKKBN to form a group of adolescent /students Care of Adolescent Reproduction Health as motivator in socializing health of adolescent reproduction at school. Kata Kunci: :Kesehatan reproduksi, ketaatan beragama, hubungan seks pranikah. Reproduction health , religiousness obedience, premarital sexual intercourse

Simulated emergence of cyclic sexual-asexual reproduction

Motivated by the cyclic pattern of reproductive regimes observed in some species of green flies (``{\it aphids}''), we simulate the evolution of a population enduring harsh seasonal conditions for survival. The reproductive regime of each female is also seasonal in principle and genetically acquired, and can mutate for each newborn with some small probability. The results show a sharp transition at a critical value of the survival probability in the winter, between a reproductive regime in the fall that is predominantly sexual, for low values of this probability, or asexual, for high values.Comment: 9 pages, 4 figures, requires RevTe

Evolution of population with sexual and asexual reproduction in changing environment

Using a lattice model based on Monte Carlo simulations, we study the role of the reproduction pattern on the fate of an evolving population. Each individual is under the selection pressure from the environment and random mutations. The habitat ("climate") is changing periodically. Evolutions of populations following two reproduction patterns are compared, asexual and sexual. We show, via Monte Carlo simulations, that sexual reproduction by keeping more diversified populations gives them better chances to adapt themselves to the changing environment. However, in order to obtain a greater chance to mate, the birth rate should be high. In the case of low birth rate and high mutation probability there is a preference for the asexual reproduction.Comment: 11 pages including figs., for Int. J. Mod. Phys. C 15, issue 2 (2004