Effect of 1-Aminocyclopropane-1-carboxylic acid and aminoethoxyvinylglycine on ethylene emanation and somatic embryogenesis from orchardgrass leaf cultures

Enhancement of somatic embryogenesis in orchardgrass leaf cultures by epinephrine

Epinephrine at 10-100 μM stimulated somatic embryogenesis from orchardgrass (Dactylis glomerata L.) leaves cultured on SH medium with 30 μM of indole-3-acetic acid (IAA). Ethylene emanation was increased at epinephrine concentrations greater than 10 μM. Decarboxylation by the leaves of [1-(14)C]IAA included in the medium was decreased almost 3-fold by 10 μM epinephrine. Epinephrine at 10 μM enhanced the number of regenerated plants on SH medium with 30 μM dicamba (SH-30). Ethylene emanation was increased by epinephrine concentrations of 500 μM and greater included in SH-30 but somatic embryogenesis was decreased. Addition of 8 μM CoCl2, 6H2O (an ethylene biosynthesis inhibitor) to medium with 500 μM epinephrine decreased ethylene emanation to the control level but did not alleviate the decreased embryogenic response.

Influence of low temperature preincubation on somatic embryogenesis and ethylene emanation from orchardgrass leaves

The objectives of this study were to determine the effects of low temperature (4 degrees C) preincubation on somatic embryogenesis from orchardgrass (Dactylis glomerata L.) leaf cultures and to relate these effects to ethylene emanation during the preincubation and incubation periods. Experiments were also conducted with an ethylene biosynthesis inhibitor aminooxyacetic acid (AOA). Segments from the innermost two leaves were cultured on SH medium with 30 micromoles dicamba at 4 degrees C for 1 to 7 d before transfer to 21 degrees C. Results from a paired design showed that the embryogenic response of leaf segments preincubated at 4 degrees C was equal or superior to nonpreincubated leaves at all time periods. Ethylene emanation was decreased during the low temperature incubation. Transfer of leaf segments from 4 degrees C to 21 degrees C was accompanied by a burst of ethylene which rose to control levels within 30 min. AOA at 20 and 40 micromoles decreased ethylene emanation but did not stimulate the embryogenic response. We conclude that the stimulation of somatic embryogenesis by low temperature is probably due to factors other than suppression of ethylene biosynthesis.

Phenylalanine ammonia-lyase, phenolic acids and ethylene in alfalfa (Medicago sativa L.) cell cultures in relation to their embryogenic ability

Phenylalanine ammonia-lyase (PAL) activity, contents of phenolic acids and ethylene production during the lag-phase, and contents of phenolic acids at the late exponential phase, showed significant differences in embryogenic (EC) and non-embryogenic (NEC) suspension cultures of Medicago sativa L. Maximum PAL activity at 6 h after inoculation was followed by an increase in the level of phenolic acids from 9.6 μg g(-1) fresh mass to 21 μg g(-1) fresh mass in NEC at 12 h. Thereafter the level of phenolic acids decreased to 5.2 μg g(-1) fresh mass at 72 h. The decline was caused predominantly by the decrease of ester-bound cinnamic acid derivatives, the decrease ranging from 83 to 20% of total phenolics. Two maxima of ethylene production were observed in NEC: the first one immediately after inoculation and the second at 6 h, coinciding with the peak of PAL activity. In NEC, most of the phenolic acids occurred in esterified form. Ability to form somatic embryos (EC) was associated with the absence of the second peak of ethylene production as well as of the peak of PAL activity at 6 h. The level of phenolic acids during the lag-phase remained low (7.2 μg g(-1) FM) and did not change. The proportion of cinnamic acid derivatives was very low (18% of total phenolics), mostly due to the extremely low level of ferulic acid. In EC, phenolic acids bound to methanol insoluble material formed the major fraction. Loss of embryogenic potential of the embryogenic culture (ECL) was associated with qualitative and quantitative changes in the contents of phenolic acids insignificantly increased PAL activity after inoculation was followed by a moderate increase in the contents of phenolic acids from 9.35 μg g(-1) fresh mass to 12.42 μg g fresh mass. A high rate of ethylene production was observed only immediately after the transfer of the culture to fresh medium. The loss of embryogenicity correlated also with changes in the relative amounts of the investigated fractions of phenolic acids. A distinct increase in the level of methoxy-substituted phenolic acids is a characteristic feature of the ECL culture.

Effect of ethylene on sanguinarine production from Papaver somniferum cell cultures

A Papaver somniferum cell line capable of producing sanguinarine equivalent to 3% of cell dry weight was used to determine if ethylene was involved in signalling the biosynthesis of this alkaloid. A 3.3-fold increase in ethylene emanation from these cell suspension cultures was observed 7 h after elicitation with a Botrytis fungal homogenate. The rate of ethylene release then decreased to near zero after 48 h, suggesting that a pulse of ethylene production may be involved in sanguinarine production. However, sanguinarine biosynthesis was not promoted when either the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), or the ethylene releasing agent, 2-chloroethylphosphonic acid (ethephon), was added to the culture. These results strongly suggest that ethylene is not intimately involved in the production of sanguinarine from Papaver somniferum cell cultures or in the transduction of the elicitation event.