Mg-chelatase H subunit affects ABA signaling in stomatal guard cells, but is not an ABA receptor in Arabidopsis thaliana

Mg-chelatase H subunit (CHLH) is a multifunctional protein involved in chlorophyll synthesis, plastid-to-nucleus retrograde signaling, and ABA perception. However, whether CHLH acts as an actual ABA receptor remains controversial. Here we present evidence that CHLH affects ABA signaling in stomatal guard cells but is not itself an ABA receptor. We screened ethyl methanesulfonate-treated Arabidopsis thaliana plants with a focus on stomatal aperture-dependent water loss in detached leaves and isolated a rapid transpiration in detached leaves 1 (rtl1) mutant that we identified as a novel missense mutant of CHLH. The rtl1 and CHLH RNAi plants showed phenotypes in which stomatal movements were insensitive to ABA, while the rtl1 phenotype showed normal sensitivity to ABA with respect to seed germination and root growth. ABA-binding analyses using 3H-labeled ABA revealed that recombinant CHLH did not bind ABA, but recombinant pyrabactin resistance 1, a reliable ABA receptor used as a control, showed specific binding. Moreover, we found that the rtl1 mutant showed ABA-induced stomatal closure when a high concentration of extracellular Ca2+ was present and that a knockout mutant of Mg-chelatase I subunit (chli1) showed the same ABA-insensitive phenotype as rtl1. These results suggest that the Mg-chelatase complex as a whole affects the ABA-signaling pathway for stomatal movements

From Waterloo to Jellalabad: The Irish and Scots at war in R Elizabeth Thompson Butler D and W. F. Butler

This essay examines the paintings of the British war artist Elizabeth Thompson Butler in conjunction with the travel, military and political writings of her husband William Francis Butler. It explores how their work both subscribes to and deviates from prevailing British imperial ideology. Elizabeth Butler produced scenes of war which eschewed jingoism and focused instead on soldiers' suffering. William Butler was an Irish Catholic officer in the British army. Despite fighting the wars of empire, he was sceptical of imperial expansion and sympathetic to Irish Home Rule objectives. Consequently, he does not conveniently fit within the categories of late Victorian imperialist or Irish Nationalist. The discussion reappraises the work of both Butlers, highlighting their sophisticated engagements with notions of war and empire from Waterloo to Afghanistan. Although William died in 1910, Elizabeth Butler lived to paint the First World War. I examine how the Butlers depict battlegrounds of Europe and empire, and address a range of colonial socio-political grievances. Close attention to their work, particularly to their shared interest in the figure of the colonial subaltern, reveals a multiplicity of narratives constituting British and Irish identities and allegiances from the late Victorian period to the First World War