Location: Plant, Soil and Nutrition ResearchTitle: Loss-of-function mutation of the calcium sensor CBL1 increases aluminum sensitivity in Arabidopsis
|LIGABA, AYALEW - Cornell University - New York|
|FEI, ZHANGJUN - Boyce Thompson Institute|
|XU, YIMIN - Boyce Thompson Institute|
|JIA, XIAOMIN - Cornell University - New York|
|SHAFF, JON - Cornell University - New York|
|LEE, SUNG-CHUL - University Of California|
|LUAN, SHENG - University Of California|
|KUDLA, JORG - University Of Munster|
Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2017
Publication Date: 4/1/2017
Citation: Ligaba, A., Fei, Z., Liu, J., Xu, Y., Jia, X., Shaff, J., Lee, S., Luan, S., Kudla, J., Kochian, L.V., Pineros, M. 2017. Loss-of-function mutation of the calcium sensor CBL1 increases aluminum sensitivity in Arabidopsis. New Phytologist. 214(2):830-841. https://doi.org/10.1111/nph.14420.
Interpretive Summary: Abiotic stress and Mineral Nutrition are major limiting factor for the world wide agronomical productivity. Over 20% of the US land area and approximately 50% of the world’s arable lands are comprised of acidic soils (pH < 5). On these acid soils, aluminum (Al) toxicity is the primary factor limiting agricultural productivity, as toxic Al damages plant root systems, ultimately resulting in a reduction of crop yields. The release of Al detoxifying organic acids from the root apex in response to Al-stress constitutes a widespread Al-tolerance mechanism by which plant roots are able to ameliorate the toxic levels of Al surrounding the growing root. The signals and cascade of events involved in perceiving the Al-stress leading to the release of organic acid is poorly understood. We used physiological and molecular approaches to identify CBL1 a key protein involved in these regulatory processes. CBL1 is a calcium binding protein that functions as a master regulator of diverse signaling networks involved in maintaining numerous physiological processes required for the proper deployment of Al resistance responses in the root. The understanding of the signaling pathways involved in the regulation of these stress response processes is essential to accurately guide breeding programs aimed at improving agriculture in marginal soils.
Technical Abstract: Despite the general physiological importance of Aluminum (Al) phytotoxicity for plants it remained unknown if and how calcineurin B-like calcium sensors (CBLs) and CBL-interacting protein kinases (CIPKs) are involved in aluminum (Al) toxicity and resistance. We performed a comparative physiological and whole transcriptome investigation of an Arabidopsis CBL1 mutant (cbl1) and the wild-type Col-0 (WT). Relative to WT, cbl1 plants exudated less Al-chelating malate, accumulated more Al, and displayed a severe root growth reduction in response to Al. Concomitantly, AtALMT1 expression, the gene encoding the malate efflux transporter mediating Al-activated malate exudation from roots, was significantly higher in WT as compared to cbl1. Particularly genes involved in metabolism, transport, cell wall modification, transcription and oxidative stress were differentially regulated between the two lines, under both control and Al stress treatments. Exposure to Al resulted in upregulation of a large set of genes only in WT and not cbl1 shoots, while a different set of genes were downregulated only in cbl1 and not WT roots. Together our analyses not only identifies CBL1 dependent constitutive transcriptional networks for maintaining adequate physiological homeostasis processes, but also reveal a high shoot-root dynamics required for the proper deployment of Al resistance responses in the root.