Characterization of two CTR-like protein kinases in Rosa hybrida and their expression during flower senescence and in response to ethylene

The expression of two CTR-gene homologues was investigated during flower senescence in two Rosa hybrida cultivars. A fragment of a gene for a protein kinase, termed RhCTR1 (GenBank Acc. No. AF271206), was amplified by PCR and used to isolate the corresponding full-length cDNA (Acc. No. AY032953) from a rose petal cDNA library. The protein RhCTR1 has 66% amino acid identity to Arabidopsis CTR1. A fragment of a second CTR homologue, termed RhCTR2 (Acc. No. AY029067) is 69% identical to the corresponding region of RhCTR1. RhCTR1 expression increased during flower senescence, while RhCTR2 was constitutively expressed during flower development. The expression of both RhCTR1 and RhCTR2 was increased in response to exogenous ethylene.     

In vitro rooting of the apple rootstock M 26 in adult and juvenile growth phases and acclimatization of the plantlets

In order to obtain optimum conditions for in vitro propagation of the apple rootstock M 26 ( Malus pumila Mill.) in adult and juvenile growth phases, several rooting experiments were performed. Supraoptimal concentrations of indole-3-butyric acid (IBA) added to the rooting media resulted in profuse callus formation. Since extensive callus production is detrimental to the survival of the plantlets, modified culture conditions were established to reduce callus formation. A reduction of the time of exposure to IBA to 5 days and, thereafter, transfer to a hormone-free medium did not eliminate callus production. Exposure to darkness during the root initiation phase increased rooting. When the rooting medium was based on the Lepoivre formula instead of the Murashige and Skoog formula, callus formation was reduced. Optimum conditions for rooting were obtained at much lower concentration than earlier reported, being 1.25 μM for the juvenile and 0.5 μM for the adult growth phase in the range of IBA concentrations tested. Anatomical studies revealed that root initials are formed after 5 days of IBA-treatment. Therefore, we transferred shoots directly to non-sterile conditions after the root-inducing phase. This resulted in a 90% survival of the plantlets. Subculture on hormone-free medium can thus be eliminated when the optimum auxin concentration is known.     

Efficient micropropagation of <Emphasis Type="Italic">Ensete ventricosum</Emphasis> applying meristem wounding: a three-step protocol

A highly efficient three-step protocol for in vitro propagation of Ensete ventricosum (enset) was developed that consisted of initiation, bud proliferation, and shoot elongation and rooting stages. At the initiation stage, it was crucial to use shoot tips (5–8 mm) with subtending corm tissues as explants to obtain growth. The addition of 0.5–1% (w/v) activated charcoal to the medium was essential to prevent phenol exudation which otherwise leads to the loss of cultures. During the bud proliferation stage, modified MS macronutrients and micronutrients together with a combination of cytokinins (1.6 M naphthaleneacetic acid, 4.4 M 6-benzylaminopurine, 23.2 M kinetin, 22.6 M N⁶ 2-isopentyladenine) was used. This novel composition of macronutrients was based on the analysis of leaf nutrient content of glasshouse-grown enset sprouts. Multiple bud formation on the enlarged corm tissue was induced only when the meristem region was wounded before transfer to the bud proliferation medium. Up to 75 healthy shoots per explant were produced, whereas unwounded explants produced, only one to two shoots per explant. A third stage with a low concentration of cytokinin enabled shoot elongation as well as root development. The plantlets were acclimatized with 100% success and they showed no apparent phenotypical deviation.Abbreviations BAP 6-Benzylaminopurine - IBA Indole-3-butyric acid - DW Dry weight - EV Ensete ventricosum medium - 2-iP N⁶ 2-Isopentyl adenine - NAA -Naphthaleneacetic acid     

A locus on mouse chromosome 6 that determines resistance to herpes simplex virus also influences reactivation, while an unlinked locus augments resistance of female mice

During studies to determine a role for tumor necrosis factor (TNF) in herpes simplex virus type 1 (HSV-1) infection using TNF receptor null mutant mice, we discovered a genetic locus, closely linked to the TNF p55 receptor (Tnfrsf1a) gene on mouse chromosome 6 (c6), that determines resistance or susceptibility to HSV-1. We named this locus the herpes resistance locus, Hrl, and showed that it also mediates resistance to HSV-2. Hrl has at least two alleles, Hrl(r), expressed by resistant strains like C57BL/6 (B6), and Hrl(s), expressed by susceptible strains like 129S6 (129) and BALB/c. Although Hrl is inherited as an autosomal dominant gene, resistance to HSV-1 is strongly sex biased such that female mice are significantly more resistant than male mice. Analysis of backcrosses between resistant B6 and susceptible 129 mice revealed that a second locus, tentatively named the sex modifier locus, Sml, functions to augment resistance of female mice. Besides determining resistance, Hrl is one of several genes involved in the control of HSV-1 replication in the eye and ganglion. Remarkably, Hrl also affects reactivation of HSV-1, possibly by interaction with some unknown gene(s). We showed that Hrl is distinct from Cmv1, the gene that determines resistance to murine cytomegalovirus, which is encoded in the major NK cell complex just distal of p55 on c6. Hrl has been mapped to a roughly 5-centimorgan interval on c6, and current efforts are focused on obtaining a high-resolution map for Hrl.     

Growth rates and biomass production of micropropagated apple plants of M26 and Gravenstein on their own roots and in different micrografted combinations under non-limiting and limiting nutrient conditions

Micropropagated apple plants of semi-dwarf rootstock M26 (M26) and vigorous cultivar Gravenstein (GR) on their own roots and different micrograft combinations were used in the experiment. The combinations included GR scion on GR root (GR/GR), M26 on M26 (M26/M26), GR on M26 (GR/M26), and M26 on GR (M26/GR). The plants were grown under non-limiting and limiting relative addition rates of nutrients. Under non-limiting nutrient conditions, M26 and GR showed a similar relative growth rate (RGR). Grafting reduced RGR significantly in the combination of M26/M26 compared to M26. The relative growth rate for the combination of GR/M26 was similar to the GR/GR plants, but it increased greatly compared to the M26/M26 plants. For the reverse combination of M26/GR, the RGR value decreased significantly compared to either the M26/M26 or the GR/GR plants. The RGR value and specific root length were lower for M26/GR than for GR/M26. No clear relationship between carbohydrate allocation and growth parameters of different plants was found under non-limiting nutrient conditions. Nutrient limitation resulted in increased dry weights and soluble sugars in the roots for all plants except for M26/GR. A reduced leaf area ratio and a lower RGR than the set relative addition rate of nitrogen were found for M26 and GR/M26 under limiting conditions. These results suggest that the dwarfing effect is not directly related to RGR of rootstocks or scions, but rather associated with root morphology of grafted plants and the ability of roots to absorb nutrients.     

Influence of IBA and aphidicolin on DNA synthesis and adventitious root regeneration from Malus ‘Jork 9’ stem discs

Adventitious root formation in Malus ‘Jork 9’ stem discs was studied through temporarily blocking DNA synthesis by application of aphidicolin (AD). Higher number of roots per disc (8.4) after 21 days of cultivation were formed after a 24-h pulse of 15 μM AD, compared to control without AD application (6.7), with significantly more roots (3.7) already appearing at day 7, compared to 1.5 roots on the control. The promotive effect of AD on rooting was lower at 5 μM, while a concentration of 30 μM was slightly inhibitory. Results show that DNA synthesis is effectively blocked by AD, and this blockage is overcome after AD withdrawal. The data indicate that AD treatment influences cell divisions, thereby, might synchronise root initiation. The effects of different treatments with and without AD were studied at the cellular level by visualising DNA replication through BrdU-labelling. BrdU labelling further revealed temporal changes in the competence of the explants to respond to applied IBA. Thus, it is shown that the proportion of replicating nuclei present during 28–32 h is significantly increased in the split IBA treatment (0–4 h and 28–32 h; treatment C3), compared with a single IBA application during 0–8 h (treatment C3.1). An erratum to this article can be found at