Ph.D. Program in Plant Molecular Biology

Friday seminar by Dr. Aditya Abha Singh

AG Lab/ Friday/ August 3, 2018/ 3.30pm/ Chloroplastic small heat shock protein HSP21 regulated heat stress response in plants.
Category: Research

Chloroplastic small heat shock protein HSP21 regulated heat stress response in plants

Aditya Abha Singh

The small heat shock proteins (sHSPs) are virtually ubiquitous proteins that are strongly induced by heat stress due to their molecular chaperone characteristics, and are considered important component of the protein quality control network. Organelle-targeted sHSPs have distinct roles in thermotolerance. A nuclear-encoded chloroplast-localized sHSP21 has been identified in diverse higher plant species. Physiological evidence suggests that this protein is involved in thermotolerance, but the molecular mechanisms of its actions, interacting companions and physiological targets largely remain unknown. It plays an important role in protecting the thermolabile PS II against heat stress by directly binding to its core subunit proteins D1 and D2 along with its GUN5-dependent retrograde signaling pathway. HSP21 imparts protection to the electron transport system by binding and stabilization of oxygen-evolving complex proteins of PSII and thylakoid membranes. Besides this, the plastidial FtsH6-HSP21 control module plays a crucial role in thermomemory. Moreover, Hsp21 is essential for chloroplast development under heat stress by its interaction with plastid nucleoid protein pTAC5 for maintaining the function of plastid-encoded RNA polymerase under heat stress. Therefore, the functionally important properties of HSP21 and the framework of mechanism of its action will be summarized.
Suggested readings
Zhong L, Zhou W, Haijun W, Ding S, Lu Q, Wen X, Peng L, Zhang L, Lu C (2013). Chloroplast Small Heat Shock Protein HSP21 Interacts with Plastid Nucleoid Protein pTAC5 and Is Essential for Chloroplast Development in Arabidopsis under Heat Stress. Plant Cell25:2925–43.

Chen ST, He NY, Chen JH, Guo FQ (2017). Identification of core subunits of photosystem II as action sites of HSP21, which is activated by the GUN5-mediated retrograde pathway in Arabidopsis. Plant J. 89:1106–1118.

Sedaghatmehr M, Muller-Roeber B, Balazadeh S (2016).The plastid metalloprotease FtsH6 and small heat shock protein HSP21 jointly regulate thermomemory in Arabidopsis. Nat. Commun. 7:12439