To find out the molecular basis of reversal of stomatal closure by Xcc, we investigated whether the activity responsible for the observed suppression of stomatal defense is secreted out of the bacteria. For this purpose, we extracted supernatants of bacterial cultures of Xcc and of rpfC and rpfF mutants with ethyl acetate. Subsequently, we investigated whether the extracts thus obtained can interfere with stomatal movements. We found that extracts from Xcc partially abolish stomatal closure induced by E. coli, Xcc (Fig. 3A), or ABA (Fig. 3B). Extracts from rpfC or rpfF mutants, however, did not have any inhibitory effect (Fig. 3, A and B). Also, Xcc extracts partially abolished ABA-induced stomatal closure in Vicia fava (Fig. 3C), a species evolutionarily distant from Arabidopsis, indicating that the factor capable of inhibiting stomatal closure probably targets some evolutionarily conserved process. In addition, we observed that the Xcc extract failed to prevent ABA-induced inhibition of light-induced stomatal opening (Fig. 3D), suggesting that the factor present in the Xcc extract acts specifically on a signaling element involved in promotion of closure by ABA. The extract did not affect the capacity of ABA to cause postgermination arrest (data not shown), which provides further evidence that it acts on some signaling component or effector required specifically for stomatal closure.

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To find out （目的）......., we investigated whether （提出问题）........ For this purpose, we （采取的方法）........ Subsequently, we investigated whether （进一步提出深层次问题）.......... We found that .（结果发现）......., however, （一些新的发现，不同寻常的发现）........ In addition, we observed that （另外还观察到）......... suggesting that （结果的意义）

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