The TATA-box binding protein-associated factor TAF12b facilitates the degradation of type-B response regulators to negatively regulate cytokinin signaling

Liu-Ming Guo; Jing Li; Pan-Pan Qi; Jie-Bing Wang; Hussein Ghanem; Ling Qing; Heng-Mu Zhang

doi:10.1016/j.xplc.2024.101076

The TATA-box binding protein-associated factor TAF12b facilitates the degradation of type-B response regulators to negatively regulate cytokinin signaling

Plant Commun. 2024 Sep 2:101076. doi: 10.1016/j.xplc.2024.101076. Online ahead of print.

Authors

Liu-Ming Guo¹, Jing Li², Pan-Pan Qi², Jie-Bing Wang³, Hussein Ghanem⁴, Ling Qing⁵, Heng-Mu Zhang⁶

Affiliations

¹ Chongqing Key Laboratory of Plant Disease Biology, College of Plant Protection, Southwest University, Chongqing 400716, China; Laboratory of Virology, Innovation Center of Chinese Medicine Crops, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
² Laboratory of Virology, Innovation Center of Chinese Medicine Crops, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China.
³ Laboratory of Virology, Innovation Center of Chinese Medicine Crops, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China; College of Life Sciences, China Jiliang University, Hangzhou 310018, China.
⁴ Chongqing Key Laboratory of Plant Disease Biology, College of Plant Protection, Southwest University, Chongqing 400716, China.
⁵ Chongqing Key Laboratory of Plant Disease Biology, College of Plant Protection, Southwest University, Chongqing 400716, China; Key Laboratory of Agricultural Biosafety and Green Production of Upper Yangtze River (Ministry of Education), Southwest University, Chongqing 400716, China; National Citrus Engineering Research Center, Southwest University, Chongqing 400712, China. Electronic address: zhhengmu@tsinghua.org.cn.
⁶ Laboratory of Virology, Innovation Center of Chinese Medicine Crops, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China. Electronic address: zhhengmu@tsinghua.org.cn.

PMID: 39228128
DOI: 10.1016/j.xplc.2024.101076

Abstract

Cytokinins (CKs) are one of important classes of plant hormones essential for plant growth and development. The TATA-box binding protein-associated factor 12b (TAF12b) is involved in cytokinin (CK) signaling, but its molecular and biochemical mechanisms remain unclear. In this study, TAF12b of Nicotiana benthamiana (NbTAF12b) was found to mediate CK response by directly interacting with type-B response regulators (B-RRs), which are positive regulators of CK signaling, and inhibiting their transcriptional activities. The co-factor specifically facilitated the proteasomal degradation of non-phosphorylated B-RRs by recruiting the KMD family of F-box proteins. Such interactions between TAF12b and B-RRs also occur in other plant species. Genetic transformation experiments further showed that overexpression of NbTAF12b attenuates the CK-hypersensitive phenotype conferred by NbRR1 overexpression. Taken together, these results suggest a conserved mechanism that TAF12b negatively regulates CK responses through promoting 26S proteasome-mediated degradation of B-RRs degradation in multiple plant species, which provides novel insights into the regulatory network of CK signaling in plants.

Keywords: TATA-box binding protein (TBP)-associated factor 12b (TAF12b); cytokinin (CK) signaling; proteasomal degradation; type-B response regulators (B-RRs).