J Integr Plant Biol. ›› 2019, Vol. 61 ›› Issue (5): 598-610.DOI: 10.1111/jipb.12766

• Research Articles • Previous Articles     Next Articles

A VPE-like protease NtTPE8 exclusively expresses in the integumentary tapetum and is involved in seed development

Wei Wang, Hanxian Xiong, Rongxin Lin, Nantian Zhao, Peng Zhao* and Meng-Xiang Sun*   

  1. State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.

    **Correspondences:
    Email: Mengxiang Sun (mxsun@whu.edu.cn, Dr. Sun is fully responsible for the distribution of all materials associated with this article); Peng Zhao (pzhao2000@whu.edu.cn)
  • Received:2018-08-27 Accepted:2018-12-17 Online:2018-12-27 Published:2019-05-01

Abstract: Programmed cell death (PCD) is an essential process for development, and shows conserved cytological features in both plants and animals. Caspases are well-known critical components of the PCD machinery in animals. However, currently few typical counterparts have been identified in plants and only several caspase-like proteases are known to be involved in plant PCD, indicating the existence of great challenge for confirming new caspase-like proteases and elucidating the mechanisms regulating plant PCD. Here, we report a novel cysteine protease, NtTPE8, which was extracted from tobacco seeds and confirmed as a new caspase-like protease. Recombinant NtTPE8 exhibited legumain and caspase-like proteolytic activities, both of which could be inhibited by the pan-caspase inhibitor (Z-VAD-FMK). Notably, NtTPE8 possessed several caspase activities and the capacity to cleave the cathepsin H substrate FVR, indicating a unique character of NtTPE8. NtTPE8 was exclusively expressed in the integumentary tapetum and thus, is the first specific molecular marker reported to date for this cell type. Down-regulation of NtTPE8 caused seed abortion, via disturbing early embryogenesis, indicating its critical role in embryogenesis and seed development. In conclusion, we identified a novel caspase-like cysteine protease, NtTPE8, exclusively expressed in the integumentary tapetum that is involved in seed development.

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