The AKT3 potassium channel protein interacts with the AtPP2CA protein phosphatase 2C.

The AKT3 potassium channel protein was identified as a strongly interacting partner of the Arabidopsis thaliana protein phosphatase 2C (AtPP2CA) in a yeast two-hybrid screen. A deletion analysis indicated that the catalytic domain of AtPP2CA was essential for the interaction with AKT3. Furthermore, the related PP2C phosphatase ABI1 did not interact with AKT3 in yeast.

Oxidative stress, heat shock and drought differentially affect expression of a tobacco protein phosphatase 2C.

A protein phosphatase 2C (PP2C)-homologous cDNA was isolated from Nicotiana tabacum (NtPP2C1). The deduced protein sequence of 416 amino acids showed the highest degree of similarity to the PP2C of Arabidopsis thaliana (AtPP2CA) implicated in abscisic acid signalling. The expression of NtPP2C1 was strongly induced by drought, but repressed by oxidative stress and heat shock. It is suggested that NtPP2C1 operates at the junction of drought, heat shock and oxidative stress.

Dual action of the active oxygen species during plant stress responses.

Adaptation to environmental changes is crucial for plant growth and survival. However, the molecular and biochemical mechanisms of adaptation are still poorly understood and the signaling pathways involved remain elusive. Active oxygen species (AOS) have been proposed as a central component of plant adaptation to both biotic and abiotic stresses. Under such conditions, AOS may play two very different roles: exacerbating damage or signaling the activation of defense responses. Such a dual function was first described in pathogenesis but has also recently been demonstrated during several abiotic stress responses. To allow for these different roles, cellular levels of AOS must be tightly controlled. The numerous AOS sources and a complex system of oxidant scavengers provide the flexibility necessary for these functions. This review discusses the dual action of AOS during plant stress responses.

Plant regeneration from embryo-derived callus in Phaseolus vulgaris L. (common bean) and P. acutifolius A. Gray (tepary bean).

Regeneration-competent callus of Phaseolus vulgaris and P. acutifolius was obtained from mature embryo explants on a medium containing thidiazuron and indole-3-acetic acid. For the P. vulgaris genotype Xan-159, regeneration was achieved from cotyledon explants, but not from embryonic axis explants. Both explants could be used for the P. acutifolius genotype NI 574 but embryonic axes gave the best results. In-vitro-rooted plantlets of P. acutifolius could readily be established in the greenhouse. For P. vulgaris hardening problems with in-vitro-rooted plantlets could be overcome by means of in vitro grafting. The potential of the described procedure for obtaining transgenic P. vulgaris plants is discussed.

[The effect of nitrovin on the kinetics of sulphadimidine in domestic fowl of different ages]. / Vliv nitrovinu na kinetiku sulfadimidinu u kura domácího ruzhého veku.

In experiment on cockerels, the interaction of sulphadimidine with nitrovin manifested itself in an effect on the distribution of sulphadimidine, and particularly on its bloodlevel; this depended, among other factors, on the age of the animals. At nitrovin medication, the bloodlevels of sulphadimidine were higher, mainly soon after administration, and their drop was quicker than in untreated animals. This effect on the levels of sulphadimidine in the blood was pronounced in three-week-old chickens, whereas in older birds it was feeble or absent. Except the higher level 30 min. after application to.five-week-old chickens given feed with 120 g t-1 of nitrovin, the differences were statistically insignificant. The changes in the concentration of sulphonamide in the liver and kidneys corresponded with the changes observed in the blood; the concentration in muscle was not affected by nitrovin under the given conditions. The favourable effect of nitrovin on weight gains, demonstrated in principle during the experiment, was directly dependent upon the concentration of nitrovin in feed. As to the effect of the length of its administratiion, the three-day administration of nitrovin (before weighing) to cockerels up to five weeks of age had a better influence on gains than administration from the sixth day after the medicated of the chickens. In older cockerels the gains were better in the groups treated for a longer time, i. e. from the sixth day from hatching.