RNAi-mediated repression of dormancy-related genes results in evergrowing apple trees

DORMANCY ASSOCIATED MADS-box (DAM) and SHORT VEGETATIVE PHASE (SVP) genes have been implicated in the regulation of winter dormancy in perennials. Ectopic expression of apple (Malus ×domestica ‘Royal Gala’) DAM and SVP genes delays budbreak and constrains lateral shoot outgrowth. In this study, we used RNAi interference (RNAi) to simultaneously target all apple DAM and SVP genes to study their role and mode of action in the regulation of bud dormancy, budbreak and flowering. A synthetic construct carrying a hairpin fragment assembled from sequences specific to coding regions of three DAM and two SVP genes was used to generate transgenic lines. Reduced expression of DAM/SVP genes resulted in delayed leaf senescence and abscission in autumn, failure to enter bud dormancy in winter, and continual growth of new leaves regardless of the season for over 3 years. Precocious flowering but normal flower morphology, fertility and fruit development were observed. The non-dormant phenotype was associated with modified phytohormone composition. The content of gibberellins (GAs) and jasmonates (JAs) was significantly increased in terminal buds of RNAi lines compared to wildtype plants, accompanied by elevated expression of the key GA biosynthesis pathway gene GIBBERELLIN 20 OXIDASE-2 (MdGA20ox-2) along with the FLOWERING LOCUS T gene MdFT2. The key mediator of plasmodesmatal closure, MdCALLOSE SYNTHASE 1 (MdCALS1) was repressed in RNAi lines. This study provides functional evidence for the role of DAM/SVP genes in vegetative phenology of apple, and paves the way for production of low-chill varieties suitable for growth in warming climates.

Programmed Cell Death Facilitates the Formation of Unisexual Male and Female Flowers in Persimmon (Diospyros kaki Thunb.)

Most varieties of persimmon (Diospyros kaki Thunb.) are gynoecious, while just a few are either monoecious, androgynomonoecious, or androecious. Persimmon flowers initially contain the original androecium and gynoecium followed by arrest of either pistil or stamen primordia before maturity. Abortion of inappropriate primordium in persimmon may be related to programmed cell death (PCD). To test this hypothesis, hematoxylin and eosin (H&E) staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, cyt-c immunohistochemistry (IHC) assay, transmission electron microscopy (TEM) observation, and real-time quantitative polymerase chain reaction (RT-qPCR) were used to clarify the occurrence and molecular regulatory mechanism of PCD in male and female floral buds during the 14 days prior to the second crucial morphological stage when inappropriate sexual primordia were arrested to form unisexual flowers. Accordingly, dead cells in inappropriate sex organs were largely accumulated during the microsporocyte and macrosporocyte period of male and female floral buds, respectively. This may explain the abortion of inappropriate sex organs, leading to unisexual flowers. PCD is necessary for normal growth and development in persimmons, as dead cells could also be observed in the normal flower organs. High levels of a gene homologous to AMC9 may have accelerated the arrest of the pistil primordium during differentiation, leading to male unisexual flowers, and high levels of genes homologous to MeGI, BAG5, AifA, and HSP70 in female floral buds were positively correlated with the arrest of stamen primordium. Future studies may try to transform unisexual flowers into hermaphroditic flowers by the regulation of PCD artificially, which will be helpful to the controlled pollination experiments.

Knowing me, not knowing you – Configural and featural processing in face and flower matching by a developmental prosopagnosic

A series of experiments investigated the extent to which a developmentalprosopagnosic, A.A., was able to use configural and featural processing to recognise faces and objects (flowers). A.A. was presented with tasks in which either configural or featural processing was selectively disrupted, by scrambling or blurring. A.A.'s face- matching performance was impaired if faces were blurred to remove their featural details, but remained comparable to that of normal controls if the faces' configural properties were disrupted by stretching. This suggests he is unable to use configural processing to recognise faces, but remains able to recognise them from featural information - consistent with Collishaw and Hole's (2000) suggestion that there are two independent "routes" to face recognition. In contrast, A.A.'s performance with blurred flowers is comparable to that of normal flower experts. AA appears to have a face-specific impairment in using configural processing that does not extend to flower recognition.

Investigating inheritance patterns of a spontaneous mutant in pigeonpea and its future implications for CGMS based hybrid breeding

Despite concerted breeding efforts directed towards genetic improvement of pigeonpea, huge gap exists between its potential and actual yields. Recently, in order to stabilize pigeonpea yield the CGMS- based system has been established in pigeonpea. Maintenance of the genetic purity of parental lines and hybrids, however, remains one the greatest challenges associated with CGMS-based system. In the context, identification of some markers clearly discriminating the parental lines and hybrids would be of immense importance. With this view, here we report the discovery of a spontaneous mutant phenotype that would act as potential visual marker in the CGMS based hybrid breeding programmes. Moreover, the nature of inheritance for the mutant phenotype was also examined. All the F1s derived from a bi-parental cross (mutant × normal) were normal with lanceolate leaves and normal flower morphology while the F2 and backcross generations segregated in ratio of 3:1 and 1:1, respectively indicating monogenic recessive inheritance of the gene(s) under investigation. More importantly, existence of a single gene affecting both traits would facilitate rapid introgression of these morphological markers into genetic backgrounds of different A-lines which will help in differentiating the CGMS-hybrids from their parental lines (A-lines). It is envisaged that these morphological markers would greatly assist pigeonpea breeders in maintaining the genetic purity while dealing with CGMS system in pigeonpea.

In vitro Propagation and Plantlet Regeneration from Doritaenopsis Purple Gem ‘Ching Hua’ Flower Explants

The effects of four types of explants removed from 10-cm flower stalks of Doritaenopsis Purple Gem ‘Ching Hua’ (immature apical flower buds, immature lateral flower buds, flower stem nodes, and flower pedicel sections) and combinations of two plant growth regulators [naphthalene acetic acid (NAA) and thidiazuron (TDZ)] on direct in-vitro shoot induction and multiplication were studied. Immature apical flower buds were the only explants that showed induction and multiplication of shoots in vitro. NAA at 5.4 and 10.7 μm combined with either 4.5 or 9.1 μm TDZ provided the fastest and greatest percentages of shoot induction (27% to 40%) and the greatest numbers of shoot multiplication (111–160 shoots per explant). In vitro–induced shoots were rooted on medium containing 5.4 μm NAA and developed into plantlets with normal vegetative and reproductive morphology. Regenerated plantlets were acclimatized, showing 100% survival and establishment in greenhouse. Plantlets were grown to maturity and showed normal flower morphology. No floral off-types were observed. The high rates of shoot multiplication obtained offer a means for mass clonal propagation of this and possibly other related Doritaenopsis hybrids.

(243) Release of New Scaevola sericea Cultivars

Scaevola sericea is a plant native to Guam. The normal flower has petals that are usually white with slight, thin, magenta bands. The seeds for these plants were collected from a parent plant with dark magenta flowers growing in the wild. Plans are to self the parent plant to observe the variation in the seedling population. Four selections of S. serica were made and are being propagated for public release. Three of these selections have white petals with broad magenta bands or spots on the flower petals, in contrast to the usual white flower. One selection has a floral fragrance.

Dwarf Flower Stalk in Onion: Characterization, Genetic Control, and Physiological Response to Ethephon and Gibberellic Acid

Recently, a dwarf scape mutant was found in `Autumn Beit-Alpha' onion (Allium cepa L.). The development of dwarf scape in onion, the genetic control of this attribute, and its response to external application of ethephon and GA3 were studied. Data from segregating populations conclusively showed that a single recessive gene, designated dw1, controls scape dwarfness in onions. Its expression is slightly modified by minor genes. Relatively slow growth and early cessation of cell elongation are the characteristics associated with scape dwarfness. A similar developmental pattern characterized emerging normal flower stalks treated with ethephon. GA3 application at 50 ppm had no effect on scape elongation of dwarf plants. In each of 3 years, dwarf genotypes always produced scapes about half the length of normal ones. The marked expression stability of the dw1 gene will facilitate its introduction into onion cultivars. Providing there is no negative pleiotropic effect, the dwarfness gene is expected to reduce lodging and, thus, improve mechanical harvest of onion seed. Chemical names used: 2-chloroethyl phosphoric acid (ethephon), gibberellic acid (GA3).

Aberrations in flower development in Silene

The occurrence of aberrant numbers of floral parts in Silene coeli-rosa was most frequent at high and low temperatures but was not obviously correlated with effectiveness of floral induction or with the growth rate of the flower. The stamens were more often aberrant than the other floral whorls. Aberrations seemed to occur independently in the different floral whorls, except in the case of the sepals and petals, since almost half the plants with aberrant numbers of sepals showed the same aberration in the petals. The findings are considered in relation to normal flower development.