부산대학교 도서관

Leaf stomata close in response to high carbon dioxide levels and open at low C[O.sub.2]. C[O.sub.2] concentrations in leaves are altered by daily dark/light cycles, as well as the continuing rise in atmospheric C[O.sub.2]. Relative to abscisic acid and blue light signaling, little is known about the molecular, cellular, and genetic mechanisms of C[O.sub.2] signaling in guard cells. Interestingly, we report that repetitive [Ca.sup.2+] transients were observed during the stomatal opening stimulus, low [C[O.sub.2]]. Furthermore, low/high [C[O.sub.2]] transitions modulated the cytosolic [Ca.sup.2+] transient pattern in Arabidopsis guard cells (Landsberg erecta). Inhibition of cytosolic [Ca.sup.2+] transients, achieved by loading guard cells with the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and not adding external [Ca.sup.2+], attenuated both high C[O.sub.2]-induced stomatal closing and low C[O.sub.2]-induced stomatal opening, and also revealed a [Ca.sup.2+]-independent phase of the C[O.sub.2] response. Furthermore, the mutant, growth controlled by abscisic acid (gca2) shows impairment in [C[O.sub.2]] modulation of the cytosolic [Ca.sup.2+] transient rate and strong impairment in high C[O.sub.2]-induced stomatal closing. Our findings provide insights into guard cell C[O.sub.2] signaling mechanisms, reveal [Ca.sup.2+]-independent events, and demonstrate that calcium elevations can participate in opposed signaling events during stomatal opening and closing. A model is proposed in which C[O.sub.2] concentrations prime [Ca.sup.2+] sensors, which could mediate specificity in [Ca.sup.2+] signaling. calcium signaling | cytoplasmic calcium | calcium specificity | stomata | Arabidopsis thaliana