Modulation of Bax Inhibitor-1 and cytosolic Ca²⁺ by cytokinins in Nicotiana tabacum cells

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• 作者：Nathalie Bolduc ; Gregory N. Lamb ; Stephen G. Cessna ; Louise F. Brisson
• 关键词：Bax Inhibitor-1 ; Calcium ; Cytokinins ; Hormones ; Programmed cell death
• 刊名：Biochimie
• 出版年：2007
• 出版时间：August 2007
• 年：2007
• 卷：89
• 期：8
• 页码：961-971
• 全文大小：851 K

文摘

The protein Bax Inhibitor-1 (BI-1) has recently emerged as a negative regulator of plant programmed cell death (PCD), but how it functions at the biochemical level remains unknown. To elucidate its regulation and mode of action, we used suspension cells of Nicotiana tabacum to study the effects of cytokinins (CKs) on the expression level of NtBI-1 via western analysis. We found that the NtBI-1 protein is up-regulated following treatments with CKs at concentrations inducing a stress response (determined by growth reduction and PR1a accumulation), but not at PCD-inducing concentrations. These data point toward a role for NtBI-1 in the stress response to CKs. Application of CKs was also accompanied by a rapid cytosolic Ca²⁺ pulse, and inhibition of this pulse with La³⁺ or EGTA partially restored viability, indicating a signaling role for Ca²⁺ in CK-induced cell death. However, CK-induced NtBI-1 accumulation was not altered by pretreatment with La³⁺, nor by treatment with several modulators of intracellular Ca²⁺ homeostasis and signaling, suggesting that CK-dependent regulation of NtBI-1 accumulation is not directly mediated by Ca²⁺.