Relation of special RNA to sensitivity of yeast strains to auxin

RNA functional in auxin action was studied in the followingfour strains of yeasts differing in their sensitivity to auxin:KV2, diploid strain of Saccharomyces ellipsoideus irresponsiveto auxin but made responsive by gibberellic acid treatment;N55, auxinresponsive mutant derived from KV2; A2-0, diploidstrain of 5. cerevisiae irresponsive even when gibberellic acidis given; and A2–N102, responsive mutant derived fromA2–0. The RNA fraction extracted from N55 and partitionedin a phenol layer sensitized KV2 to auxin. This kind of RNAwas not detected in KV2 cells. The functional RNA from N55 wasof low molecular weight, as was functional RNA isolated fromgibberellic acid-treated Jerusalem artichoke tuber. Gibberellicacid-treated KV2 cells have been known to contain RNA whichfunctions similarly to the RNA mentioned above. Both A2–0and A2–N102 contained RNA which made KV2 cells responsiveto auxin. Some factors other than functional RNA may determinethe difference in the sensitivity to auxin between A2–0and A2–N102. (Received August 20, 1968; )     

Induced Production of a Sexual Hormone in Yeast

We have already described that α hormone excreted by α type cells expands cells of α type specifically and α hormone excreted by α type cells expands α type cells in Saccharomyces terevisiae. Both substances are steroidal compounds. In the present experiment the third hormonal substance has been found. a Hormone induced excretion of a methylene chloride-insoluble substance which expands a type cells specifically, when added to a type cells. Testosterone showed the same type of action as that of a hormone. On the other hand, a hormone did not show an action to induce excretion of methylene chloride-insoluble hormonal substance, when added to a type cells. Relation among three hormonal substances described above seems to be important to make clear the mating process of the yeast.     

Responsiveness of yeast cells to auxin in relation to cell age

Using Urografin density gradient centrifugation, we fractionatedcells in a stationary culture of a homothallic strain, D6-0,of Saccharomyces cerevisiae and obtained two groups; a largecell fraction (L fraction) and a small cell fraction (S fraction).Indole-3-acetic acid (20 mg/liter) expands cells of the S fractionbut not those of the L fraction. Differences in the physiologicalnature between the two fractions were studied in relation totheir responsiveness to auxin. In general, L cells contain largeramounts of DNA, RNA and protein per cell than do S cells. Whencells of the two fractions were transferred to a nutrient medium,S fraction showed a longer lag period than L fraction beforebuds appeared on cells. Preceding cell division, cells of Sfraction enlarged significantly, while cells of L. fractionenlarged only slightly. In the 4 hr following inoculation, DNAcontent per culture doubled in the L fraction while the increasewas very small in the S fraction. Electron microscopy revealedthat cell walls were thicker in the S fraction than in the Lfraction. Development of mitochondria and other intracellularmembraneous structures was poorer in cells of the S fractionthan in those of the L fraction. The relationship between thecell generation cycle and responsiveness to auxin is discussed. (Received March 11, 1971; )     

Effects of antimetabolites on flowering in Arabidopsis

Effects of five kinds of antimetabolites on flowering in Arabidopsiswere studied. 8-Azaguanine, acriflavine, ethidium bromide andstreptomycin accelerated flowering but cycloheximide did not.The accelerating effect of 8-azaguanine was reversed by guanine. (Received April 30, 1971; )     

Role of Cell Wall-degrading Enzymes in Auxin-induced Cell Expansion in Yeast

Using auxin-responsive diploid strains of Saccharomyces cerevisiae and S. ellipsoideus, we studied the role of cell wall-degrading enzymes in the auxin-induced cell expansion. Highly purified fungal β-l,3-glucanase added to cell suspension caused cell expansion in these strains. The cell expansion induced by auxin was inhibited by the addition of õ-glucono-lactone, which inhibited the activity of a crude β-l,3-gluca-nase preparation from yeast in a competitive manner. Laminarinase activity was significantly higher in the extract from auxin-treated yeast cells than in the extract of cells not treated with auxin. These results support the idea that auxin induces expansion of yeast cells of certain strains through enhancement of the activity of wall polysaccharide-degrading enzymes.