The Effect of Calmodulin Antagonists on Gibberellic Acid-induced Enzyme Secretion in Barley Aleurone Layers

Calmodulin activity was detected and assayed in barley aleuronecells. The effect of calmodulin antagonists on GA₃-induced enzymesynthesis and secretion in barley aleurone layers was also investigated.These calmodulin antagonists (chlorpromazine, haloperidol) inhibitedonly GA₂-induced -amylase secretion. This inhibitory effectwas intensified after 6 h of GA₃-incubation. This leads us tosuggest that some calmodulin-controlled mechanism is involvedin GA₂-induced -amylase secretion. Hordeum vulgare L., barley aleurone cells, gibberellic acid, -amylase secretion, calmodulin, calmodulin antagonist     

BLUE AND NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN CONIDIAL DEVELOPMENT OF THE FUNGUS, ALTERNARIA TOMATO

In the sporulation of Alternaria tomato, conidiophores are induced by near ultraviolet irradiation but not by darkness, and the conidia develop only when the irradiation is followed by a period of darkness. Conidial development is suppressed by a short exposure to blue light at a definite time during the dark period following the inductive irradiation. The suppression of conidial development by blue light can be reversed by exposure to near ultraviolet light immediately following the blue light irradiation. This reversion is reversibly suppressed by a further exposure to blue light immediately following near ultraviolet irradiation. Thus, at least two stages are involved in the sporulation of A. tomato, the first being a photochemical stage necessary for the induction of conidiophores, and the second essential for the conidial development which proceeds only in the absence of exposure to the blue region of the spectrum. Moreover, conidial development can be controlled by alternating doses of blue and near ultraviolet light, and the subsequent response depends upon the last kind of radiation given. It is concluded that a new pigment system, which we have named “Mycochrome”, is involved in the blue and near ultraviolet reversible photoreaction, and that this compound plays an important role in the photocontrol of conidial development in this fungus.     

The action of skeleton photoperiods on flowering in Lemna perpusilla

The effects of 24 hr cycle skeleton photoperiodic schedulesinvolving two short light pulses on flowering in Lemna perpusillahave been studied. Simulation of complete photoperiods by correspondingskeletal ones is nearly perfect for all photoperiods up to 8hr and is unstable for periods of 9 to 13 hr. A jump in theresponse phase appears when skeleton photoperiods ranging from12 to 13hr are given. For all skeleton photoperiods longer than14 hr the phase is entrained so that it agrees with that givenby skeleton photoperiods of complemental lengths. That is, askeleton photoperiod of 18 hr is equivalent to that of 6 (=24–18) hr. Simulation is largely related to whether thesecond pulse is locked on to "dawn" or to "sunset" dependingon when it falls during the dark period following the firstpulse. The inductive action of skeleton photoperiods that gives unstableentrainment depends on the length of a preliminary dark periodgiven before the plant receives the first pulse, since in theseskeleton schedules the sensitive zone to the second pulse shiftswith the length of the preliminary darkness. Thus, we tentatively conclude that the circadian oscillationin L. perpusilla involves an entrainment mechanism and thatphotoperiodic induction is contingent on the coincidence oflight and a specific inductive phase in oscillation. (Received September 18, 1968; )     

PHOTOSYNTHETIC NITRITE REDUCTASE FROM SPINACH

Photosynthetic nitrite reductase (PNiR) was purified extensivelyfrom spinach leaves by the method including acetone precipitation,ammonium sulfate fractionations and DEAE-cellulose column chromatography.The purified PNiR had the highest specific activity thus farobtained. Absorption spectrum of the purified PNiR indicatedthat it had no flavin component. There was no difference inthe rate of photosynthetic nitrite reduction between aerobicand anaerobic conditions. In chloroplasts two reductase systems related with ferredoxinhad been recognized, which were ferredoxin-nitrite and ferredoxin-NADPreductase system. The relationship between the two systems wasinvestigated by using the reconstituted enzyme system. Whenthe reduction of NADP was taking place, the reduction of nitritewas strongly inhibited. Some physiological significance of thephenomenon was discussed. ¹This work was mainly perfomed in the Department of Cell Physiology,University of California, during the author's stay, and waspresented in the 6th annual meeting of the Japanese Societyof Plant Physiologists on April 4-7, 1964 in Tokyo.     

An action spectrum for photoinduced sporulation in the fungus Trichoderma viride

When a dark grown colony of Trichoderma viride is exposed towhite light for a short time, sporulation occurs only in thenarrow region of mycelia produced just prior to illumination.The action spectrum of this light effect was obtained for wavelengthsbelow 520 mµ using monochromatic irradiation of knownintensity having a band width of 10 mµ. The action spectrumshows 4 distinct peaks at 320, 380, 430 and 480 mµ. Thewavelengths at 320 and 380 mµ are most effective in photoinducedsporulation. The longer wavelengths, 430 and 480 mµ, areconsiderably less effective. The possibility that a carotenoid or a flavin compound may bea photoreceptor in this photoinduced sporulation is discussed. (Received January 4, 1969; )     

TWO LIGHT REACTIONS IN THE PHOTOPERIODIC CONTROL OF FLOWERING OF LEMNA PERPUSILLA AND L. GIBBA

The effects of light quality on the photoperiodic control inthe flowering of a SD duckweed, Lemna perpusilla strain 6746,and a LD duckweed, L. gibba strain G3, were investigated withspecial reference to the interaction between R and B or FR lights. In the diurnal alternation of R or G light and dark periods,L. perpusilla responded as a SDP, but in that of B or FR lightit was almost daylength-indifferent. On the other hand, L. gibbaresponded as a LDP under B, R or FR light, although the criticallight length was altered by the light quality. In the diurnal alternation of R and B or FR light periods containingno dark period, L. perpusilla flowered with the shortening ofthe optimal and critical R light lengths, compared with theplant exposed to that of R light and dark period. The floweringresponse of L. gibba to the R light length showed double peaks,that is, the first peak at the R duration less than 9 hours,and the second at the R duration longer than 9 hours. The firstpeak corresponds to the optimal R light length in L. perpusilla. Under the CL with a mixture of R and B or FR lights, the floweringand frond production were influenced by the intensity ratioof two light given. In both plants, the optimal ratio of B toR or FR to R for the flowering was always greater than thatfor the frond production. It is suggested that the B or FR light interacts with the Rlight in the photoperiodic process in the plants and this interactionbetween the R and B or FR lights should be of importance forobtaining a better understanding of photoperiodism. (Received August 28, 1965; )     

EFFECT OF POLYOXIN ON THE MORPHOGENESIS OF THE FUNGUS, ALTERNARIA TOMATO WITH SPECIAL REFERRENCE TO PHOTOSPORULATION

Photosporulation of Alternaria tomato was very little influenced by polyoxin at concentrations below 10 μg/ml, although hyphae and conidia were morphologically affected. The hyphae grown in the presence of polyoxin were easily disrupted.