Auxin-facilitated utilization of glutamic acid by tobacco crown-gall teratoma cells

Teratoma tissues obtained by inoculating Nicotiana tabacum cv. "Turkish" with a moderately virulent strain of the crown-gall bacterium require the synthetic auxin, α-naphthaleneacetic acid (NAA) when glutamic acid is used as a sole nitrogen source in the culture medium. In contrast, growth on culture media containing ammonium ion, nitrate ion or glutamine as an N source does not require NAA. Moreover, added NAA does not stimulate teratoma tissue grown on these N sources. Glutamic acid did not inhibit growth of teratoma tissue on media containing NO 3 (-) . Growth on mixtures of glutamic acid and NO 3 (-) was additive in the presence of NAA indicating that NAA promotes the utilization of glutamic acid in the culture medium. Increased concentration of potassium ion in the culture medium was required for growth on glutamic acid in the absence of added auxin. K(+) did not stimulate growth on glutamine. When teratoma tissues were grown on media containing glutamic acid and varying concentrations of both K(+) and NAA increasing concentrations of NAA reduced the stimulating effect of K(+) and, conversely, increasing concentrations of K(+) reduced the stimulating effect of NAA. It is concluded that K(+) and auxin act either directly or indirectly at a common site to promote glutamic acid utilization.