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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #343918
Title: Heterodimerization of Arabidopsis calcium/proton exchangers contributes to regulation of guard cell dynamics and plant defense responses

Author
item HOCKING, BRADLEIGH - University Of Adelaide
item CONN, SIMON - University Of Adelaide
item MANOHAR, MURLI - Children'S Nutrition Research Center (CNRC)
item XU, BO - University Of Adelaide
item ATHMAN, ASMINI - University Of Adelaide
item STANCOMBE, MATTHEW - University Of Cambridge
item WEBB, ALEX - University Of Cambridge
item HIRSCHI, KENDAL - Children'S Nutrition Research Center (CNRC)
item GILLIHAM, MATTHEW - University Of Adelaide

Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2017
Publication Date: 6/22/2017
Citation: Hocking, B., Conn, S.J., Manohar, M., Xu, B., Athman, A., Stancombe, M.A., Webb, A.R., Hirschi, K.D., Gilliham, M. 2017. Heterodimerization of Arabidopsis calcium/proton exchangers contributes to regulation of guard cell dynamics and plant defense responses. Journal of Experimental Botany. doi:10.1093/jxb/erx209.

Interpretive Summary: Transporters move nutrients and toxic metals to different organs within plants. We aspire to manipulate these transporters to enhance nutrients into edible portions of the plant or remove potentially toxic metals from these same tissues. In this study we characterize multiple transporters that are expressed in plants and analyze how the transporters cooperate to sequester nutrients and toxins. Our findings provide valuable information regarding the interactions among transports. This work provides a roadmaps to engineer the transport of nutrients in agriculturally important crops.

Technical Abstract: "Arabidopsis thaliana" cation exchangers (CAX1 and CAX3) are closely related tonoplast-localized calcium/proton (Ca(2+)/H+) antiporters that contribute to cellular Ca(2+) homeostasis. CAX1 and CAX3 were previously shown to interact in yeast; however, the function of this complex in plants has remained elusive. Here, we demonstrate that expression of CAX1 and CAX3 occurs in guard cells. Additionally, CAX1 and CAX3 are co-expressed in mesophyll tissue in response to wounding or flg22 treatment, due to the induction of CAX3 expression. Having shown that the transporters can be co-expressed in the same cells, we demonstrate that CAX1 and CAX3 can form homomeric and heteromeric complexes in plants. Consistent with the formation of a functional CAX1-CAX3 complex, CAX1 and CAX3 integrated into the yeast genome suppressed a Ca(2+)-hypersensitive phenotype of mutants defective in vacuolar Ca(2+) transport, and demonstrated enzyme kinetics different from those of either CAX protein expressed by itself. We demonstrate that the interactions between CAX proteins contribute to the functioning of stomata, because stomata were more closed in cax1-1, cax3-1, and cax1-1/cax3-1 loss-of-function mutants due to an inability to buffer Ca(2+) effectively. We hypothesize that the formation of CAX1-CAX3 complexes may occur in the mesophyll to affect intracellular Ca(2+) signaling during defense responses.