Aging progression involving dwarfism and its acceleration by red light in bean hypocotyls

The effect of red light on the aging progression of the bean (Phaseolus vulgaris L.) hypocotyl segment unit was examined in relation to dwarfism using Kentucky Wonder (tall) and Masterpiece (dwarf) varieties. In both plants, red light promoted the elongation of younger zones and inhibited that of mature zones. The zone exhibiting maximum elongation was shifted to the younger zones by red light irradiation regardless of the plant type, but its extent was greater in the dwarf than in the tall. Thus, red light hastens both the beginning of elongation in the younger portion and its termination in the mature portion of the hypocotyl, particularly of the dwarf plant. These red light responses in each zone of both the tall and dwarf hypocotyl units were reversed by subsequent exposure to far red light regardless of the duration and intensity of red light, thus indicating that the hastened aging progression of the hypocotyl by red light is mediated by phytochrome. However, there is no difference in the rate of decay of Pfr between the tall and dwarf hypocotyls.     

Sun angle time windows for absconding by the dwarf honeybee, Apis florea

In Asia, the red dwarf honeybee, Apis florea, is notorious for its absconding habit. Interestingly, such colonies show a bimodal frequency distribution about a noonday lull throughout the year. Because slight errors in reading the relative position of the sun near its zenith results in very large orientation errors in the waggle dances of other honeybees in the tropics, we postulated that the frequency distribution of absconding in the red dwarf honeybee relative to local clock time could be explained in similar fashion. The frequency distribution of absconding by the red dwarf honeybee with respect to time was found to be bimodal with a pronounced lull at noonday, which in turn is related to the altitude angle of the sun. So, these bees largely avoid flying off between 12:00 h and 13:00 h on the one hand and that their preferred departure angle of the sun is between 55° and 65° on the other. Given the difficulties of taking an accurate reading of the sun at angles ±6° of the sun's zenith (resulting in a 1 h loss around noon) and the 2 h required to reach consensus over the final direction to be flown, the bees are simply left with two time windows, morning and afternoon, in which to abscond and, indeed some 90% of the red dwarf honeybee colonies do so. The noonday lull is not associated with high temperatures for any given day. Absconding is not inhibited by high temperatures.     

Differential Responses to Hunting in Two Sympatric Species of Brocket Deer (Mazama americana and M. nana)

Hunting by humans may affect the abundance and activity patterns of game species. We examined the effect of hunting on the abundance and activity patterns of sympatric red brocket deer Mazama americana and dwarf brocket deer M. nana . We conducted four camera-trap surveys (158 sampling stations, 10,244 trap-days, total area sampled 1200 km²) in three areas within the Atlantic Forest of Misiones, Argentina, that differ in protection and hunting pressure. We used logistic regression and tests of independence to evaluate if protection, hunting pressure, and other independent variables affect the probability of recording each species and their recording rate. We used the Mardia–Watson–Wheeler test to examine if the daily activity pattern differs between species and changes with hunting pressure. Red brocket deer were more frequently recorded (397 records, 58% of stations) than dwarf brocket deer (100 records, 37% of stations). The probability of recording red brockets was higher in areas with better protection and increased with the distance to the main accesses used by poachers. The probability of recording dwarf brockets was higher in areas with low protection. Red brockets were more nocturnal than dwarf brockets, a difference that may reduce interspecific competition. However, red brockets were more diurnal in the best-protected areas, suggesting that they can adjust their activity to local hunting pressure. Hunting has opposite effects on the abundance of these deer and may facilitate their coexistence. Hunting should be carefully controlled or managed to ensure the conservation of these little known species.     

A new growth inhibitor, pisumin, involved in light inhibition of epicotyl growth of dwarf peas

A new growth inhibitor, tentatively named pisumin, which increased under red light and remained at initial level or decreased when dwarf pea (Pisum sativum L. cv Progress No. 9) seedlings were transferred from red light to dark, has been isolated in the form of a colorless powder from light-exposed epicotyls of dwarf peas, and characterized partially as an aliphatic carboxylic acid (molecular weight 284) by spectrometric analyses.

Exogenous pisumin inhibited the growth of epicotyl segments of dwarf peas at concentrations higher than 0.1 millimolar in the dark.

     

Abscisic acid in pea shoots

Summary The (+)-abscisic acid content of pea shoots has been determined using gas-liquid chromatography. In both tall and dwarf cultivars no significant difference was observed between plants grown in the dark or under red light. Nor was the difference between the tall and dwarf cultivars themselves significant.     

Extrasolar terrestrial planets and possibility of extraterrestrial life]

Recent development of research on extrasolar planets are reviewed. About 120 extrasolar Jupiter-mass planets have been discovered through the observation of Doppler shift in the light of their host stars that is caused by acceleration due to planet orbital motions. Although the extrasolar planets so far observed may be limited to gas giant planets and their orbits differ from those of giant planets in our Solar system (Jupiter and Saturn), the theoretically predicted probability of existence of extrasolar terrestrial planets that can have liquid water ocean on their surface is comparable to that of detectable gas giant planets. Based on the number of extrasolar gas giants detected so far, about 100 life-sustainable planets may exist within a range of 200 light years. Indirect observation of extrasolar terrestrial planets would be done with space telescopes within several years and direct one may be done within 20 years. The latter can detect biomarkers on these planets as well.     

Changes in concentration of endogenous growth inhibitors during growth recovery of dwarf pea seedlings

In order to clarify the role of endogenous growth inhibitors A-2α and A-2β in a dwarf pea plant, red light (emission peak 657 nm) treated, 9-d-old seedlings of dwarf pea (Pisum sativum L. cv. Progress No. 9) were transferred to darkness, and the resulting changes in growth rate and concentrations of A-2α and A-2β were monitored. The growth rate of the epicotyls increased, and the concentration of the inhibitors in the epicotyls decreased, according to sigmoidal time courses. The relationship between the logarithms of the concentration of the inhibitors and the corresponding growth rate was linear. These results suggest that A-2α and A-2β, may play an important role in the growth recovery process of the dwarf pea cultivar after termination of red light irradiation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Gibberellic Acid-Promoted Lignification and Phenylalanine Ammonia-lyase Activity in a Dwarf Pea (Pisum sativum)

The effects of gibberellic acid on lignification in seedlings of a dwarf and a tall cultivar of pea (Pisum sativum) grown under red or white light or in the darkness, were studied. Gibberellic acid (10⁻⁶-10⁻⁴ m) promoted stem elongation in both light and dark and increased the percentage of lignin in the stems of the light-grown dwarf pea. The gibberellin had no effect on the lignin content of the tall pea although high concentrations (10⁻⁴ m) promoted growth of the tall plants. Time course studies indicated that the enhanced lignification in the gibberellin-treated dwarf plants occurred only after a lag period of several days. It was concluded that gibberellic acid-enhanced ligmification had no direct relation to gibberellic acid-promoted growth. The activity of phenylalanine ammonia-lyase (E.C. 4.3.1.5) was higher in gibberellin-treated dwarf plants grown under white or red light than in untreated dwarf plants. Gibberellic acid had no detectable effect on the activity of this enzyme when the plants were grown in darkness, just as it had no effect on lignification under dark conditions. The data suggest that in gibberellin-deficient peas the activity of phenylalanine ammonia-lyase is one of the limiting factors in lignification.     

Detection of Sap-Transmissible Viruses by ELISA in Tissue-Propagated Plants of Red Raspberry during in vitro Culture

Apple mosaic virus and raspberry bushy dwarf virus were detected by ELISA in plantlets of red raspberry still growing in vitro. The plantlets were derived from explants which were excised from plants infected by either of the viruses mentioned. Detection by ELISA of prune dwarf virus in 4-month-old in vitro cultures of sour cherry was reported earlier. Thus, application of ELISA to tissue cultured plants in vitro seems to be an appropriate method for early detection of virus-infected plant cultures.     

Phenotypic Analysis of a Dwarf Wheat (Triticum aestivum L.) with Altered Phytochrome-Mediated Growth Responses

The influence of the amount of red light relative to far red light (red/far red ratio) on leaf-sheath elongation, leaf length, tillering, assimilate partitioning to shoots and roots, and chlorophyll content in a dwarf wheat (Triticum aestivum L. cv Tibet Dwarf) and seven other dwarf and standard cultivars was determined. All cultivars tested showed far red-stimulated leaf and leaf-sheath elongation except Tibet Dwarf. Tibet Dwarf was also unresponsive to a brief end-of-day exposure to far red light, although the other cultivars exhibited increased leaf-sheath and leaf length. In these cultivars, the effects of an end-of-day 5-min far red exposure were reversible by a subsequent 5-min red light exposure. Shoot/root ratios were higher and tillering was suppressed by increased far red irradiance in all cultivars except Tibet Dwarf. In addition, Tibet Dwarf was less responsive to dark-induced leaf and leaf-sheath elongation (etiolation) and retained chlorophyll in dark-adapted leaves longer than control cultivars. Tibet Dwarf did not differ from the other cultivars in leaf chlorophyll content. Western blot analysis, using an antibody against phytochrome A, showed that dark-grown Tibet Dwarf shoots contained at least twice the amount of detectable phytochrome A protein present in the other wheat cultivars. These results, plus the short, thick-stemmed, dark-pigmented phenotype of Tibet Dwarf suggest the possibility of a mutation in the phytochrome/signal transduction pathway.     

SSR markers reveal the population structure of Sri Lankan yellow dwarf coconuts (<Emphasis Type="Italic">Cocos nucifera</Emphasis> L.)

World coconut germplasm has been classified broadly as tall and dwarf coconuts based on palm stature. Dwarf coconuts are predominantly self-breeding purelines hypothesised to have derived from tall coconuts. Dwarfs are categorized as yellow, green, red and brown on the colour of epicarp and are important as parents in hybridization of coconuts for desirable traits. Sri Lankan yellow dwarfs (SLYD) were observed to have uncommon phenotypes which were not previously reported for dwarf coconuts in the world, and this study was conducted to elucidate the population structure of SLYD. One hundred and two randomly selected SLYD individuals were categorized into three morphological groups and their genotypes were derived at 30 SSR loci. Genotypic data were analysed in PowerMarker 3.2.5 and Structure 2.3.4 software to derive the genetic diversity and the population structure. Unexpectedly high numbrs of alleles, genotypes, gene diversity and heterozygosity values were recorded for SLYD. Four populations were identified within SLYD under admixture model and their morphological variations were determined. Cross pollination between the dwarf and tall coconut varieties followed by the fixing of alleles by subsequent self-pollination was hypothesised to be the cause for the emergence of new genetic groups within dwarf populations. The study demonstrated the formation of new genotypes upon limited cross pollination of even naturally self-pollinating tree crops. The information will be useful for developing strategies for germplasm conservation, practical coconut breeding and determining the domestication and evolution of dwarf coconuts.     

Which Type of Planets do We Expect to Observe in the Habitable Zone?

We used a sample of super-Earth-like planets detected by the Doppler spectroscopy and transit techniques to explore the dependence of orbital parameters of the planets on the metallicity of their host stars. We confirm the previous results (although still based on small samples of planets) that super-Earths orbiting around metal-rich stars are not observed to be as distant from their host stars as we observe their metal-poor counterparts to be. The orbits of these super-Earths with metal-rich hosts usually do not reach into the Habitable Zone (HZ), keeping them very hot and inhabitable. We found that most of the known planets in the HZ are orbiting their GK-type hosts which are metal-poor. The metal-poor nature of planets in the HZ suggests a high Mg abundance relative to Si and high Si abundance relative to Fe. These results lead us to speculate that HZ planets might be more frequent in the ancient Galaxy and had compositions different from that of our Earth.     

Endogenous gibberellins of a radiation induced single gene dwarf mutant of bean

The distribution of endogenous gibberellins in Dwarf-1, a single gene dwarf mutant of Mexico 80-R red beans, was studied. Parallel extraction and fractionation of seeds of this mutant and those of a normal homozygous line followed by thin layer chromatography and bioassays using Rumex obtusifolius, wheat seed endosperm and dwarf bean plants revealed that a stem elongation control factor was contained in the non-acidic fraction from normal, but not from Dwarf-1, seeds. It was concluded that the single gene mutation causes a block either in gibberellin precursor formation or in production of a non-acidic fraction gibberellin-like substance.     

Isolates of raspberry bushy dwarf virus differing in Rubus host range

Isolates of raspberry bushy dwarf virus (RBDV) occurring in the field at East Mailing Research Station (EMRS), and an isolate from raspberry seed imported from the USSR, were found to differ from the Scottish type isolate (D200) of RBDV in that they infected red raspberry cultivars that are resistant, possibly immune, to isolate D200. Of several red raspberry, blackberry and hybrid berry cultivars and EMRS raspberry selections graft-inoculated with these recently discovered RBDV isolates only two raspberry cvs (Haida and Rannaya Sladkaya) and one EMRS selection did not become infected. Differences in the conclusions reached in two previous studies on the inheritance of resistance to RBDV in raspberry can be explained by the use of virus isolates that differed in Rubus host range.     

The role of xanthoxin in the inhibition of pea seedling growth by red light

Intermittent periods of red light illumination inhibit the growth of dwarf pea seedlings within 1 day and stop length increase completely in 3 days. Cis,trans-xanthoxin is synthesized within the plant during the 1st day of illumination and reaches a maximum level on the 3rd day. The red light treatment also causes an increase in the levels of violaxanthin, linoleic acid and peroxidase, lipoxygenase and carotene-bleaching activities in the plant. The possible control of xanthoxin production is discussed.     

Thermodynamics of thermal radiation from stars photoautotrophs and biospheres

Photoautotrophs are almost the exclusive providers of chemical free energy to the Earth biosphere. Their importance in coadjuvating the evolutionary development of higher forms of life in other planets is briefly discussed from this point of view. A simple analysis based on the nonequilibrium thermodynamics of thermal radiation fields is performed. The analysis relates well known standard parameters of stars of the main sequence to the thermodynamic bounds on the free energy acquisition of planetary photosynthetic processes activated by the star radiation. Upper bounds to permissible wavelengths, active in photosynthesis easily follow. Simple inferences can then be made about the possible types of main sequence stars with planetary systems where exobiological photoautotrophs might have evolved. As red dwarves constitute both the great majority of companions to the Sun and the majority of main sequence stars in our Galaxy, emphasis is placed on discussing the case of planetary systems of stars with low photospheric temperatures. Bounds to the free energy intake per unit area by the biospheres of planets in planetary systems of late type main sequence stars are estimated and compared. Some simple conclusions are drawn.Special Symposium on Photochemistry and the Origins of Life, Sixth International Congress on Photobiology, Bochum, Germany.     

HABITABLE ZONES AROUND LOW MASS STARS AND THE SEARCH FOR EXTRATERRESTRIAL LIFE

Habitable planets are likely to exist around stars nottoo different from the Sun if current theories about terrestrialclimate evolution are correct. Some of these planets may have evolved life, and some of the inhabited planets may have evolved O₂-rich atmospheres. Such atmospheres could be detectedspectroscopically on planets around nearby stars using a space-based interferometer to search for the 9.6m band of O₃.Planets with O₂-rich atmospheres that lie within the habitable zone around their parent star are, in all probability, inhabited.     

Meiotic nondisjunction and translocation segregation in dwarf (dw/dw) and control T(1;13)70H heterozygous mice

The meiotic behavior of translocation heterozygous T70 (1;13)H/+ male mice with a Snell dwarf (dw/dw) genotype was compared with that of nondwarf T70H/+ controls. A four-fold increase in the nondisjunction frequency of the normal bivalents occurred as a consequence of the dwarf genotype. This increase is identical to that seen in karyologically normal dwarf males. No effect of the dwarf condition on the segregation of the translocation multivalent could be noted. Thus, translocation heterozygosity does not enhance the meiotic instability caused by the hypopituitary dwarf condition. From a small sample of oocytes from T70H/+ and chromosomally normal dwarf females it is concluded that nondisjunction in females is not increased by the dwarf condition. In general we conclude that animals with higher spontaneous nondisjunction levels are not necessarily more sensitive to factors increasing nondisjunction.     

Purification of carrot red leaf virus and evidence from four serological tests for its relationship to luteoviruses

Carrot red leaf virus (CRLV) was purified from infected chervil by centrifuging whole plant extracts at low speed and incubating the resuspended pellets with Driselase; the digest was then treated with 1% (v/v) Triton X-100 and the virus concentrated by centrifugation twice at high speed through a layer of 20% sucrose. The preparations (about 1 μg virus/g tissue) contained isometric particles c. 25 nm in diameter which formed a single u.v.-absorbing component in sucrose density gradients. Chervil seedlings exposed to aphids (Cavariella aegopodii) that had been injected with or had fed on fractions from the u.v.-absorbing zone developed typical symptoms of infection with CRLV. CRLV particles had a sedimentation coefficient (s_20,w) of 104 S, buoyant density in CsCl of 1.403 g/cm³ and A₂₆₀/A₂₈₀ of 1.62. Antiserum with a gel-diffusion titre of 1/512 was obtained from a rabbit injected intradermally with 100 μg purified virus. CRLV was detected by immunosorbent electron microscopy and enzyme-linked immunosorbent assay in extracts of the petioles and leaf midribs of infected chervil and in groups of five to 20 viruliferous C. aegopodii. Analysis of antiserum/virus reactions by density gradient centrifugation showed that CRLV is distantly related to all luteoviruses tested; its relationships were closest to barley yellow dwarf virus (RPV strain), and perhaps also to beet western yellows virus, more distant to tobacco necrotic dwarf, potato leafroll and bean leafroll viruses, and very distant to barley yellow dwarf (MAV strain) and soybean dwarf viruses. Some of these relationships were detected by double diffusion in agarose gels and by electron microscopy of antiserum/virus mixtures. Immunosorbent electron microscopy detected all these relationships but suggested that CRLV was more closely related to tobacco necrotic dwarf and potato leafroll viruses than to barley yellow dwarf virus (RPV strain). The results show that CRLV should be considered a definitive member of the luteovirus group, and provide confirmation of recent evidence that potato leafroll virus is a luteovirus.     

伴性矮小型鸡GH、GHR和IGF-1基因的表达变化

采用荧光实时定量PCR的方法, 从转录水平上分析了伴性矮小型鸡和普通鸡肝脏中GH、GHR和IGF-1基因的表达变化趋势。结果表明：伴性矮小型鸡和普通鸡肝脏组织中GH的mRNA表达量没有明显差异, 而GHR在矮小鸡中的表达量明显比普通鸡的高3倍多, 但IGF-1基因在矮小鸡肝脏中的表达量却远远低于普通鸡, 差异达到2个数量级。这表明, 伴性矮小型鸡GHR外显子10 和3′非翻译区的长片断缺失并没有降低GHR基因的表达, 相反有所增高, 这一过程中可能存在相应的功能代偿机制。与此同时, 在伴性矮小型鸡肝脏中几乎观察不到IGF-1基因的表达, 证明正是由于GHR基因的缺陷影响了GH生理效应的发挥。实验结果印证了伴性矮小表型与GH和GHR的转录水平无关, 而可能是GHR编码产物异常阻碍了GH-GHR-IGF信号通路, 导致IGF-1表达受阻, 不能发挥正常的生理功能。