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. 2019 Dec 6;18(5):1317–1329. doi: 10.1111/pbi.13297

Figure 7.

Figure 7

A hypothetical working model for the role of OsNTL3 in heat‐induced ER stress response in rice. Under normal growth condition, the OsbZIP74 precursor protein (bZIP74P) localizes in ER membrane while the OsNTL3 precursor protein (NTL3P) is found in plasma membrane. In response to heat stress, accumulation of misfolded proteins in ER leads to activation of the ER‐localized OsIRE1, which has both protein kinase and endonuclease domains. Twenty nucleotides in the double‐stem structure of OsbZIP74 mRNA are spliced out and an open reading frame shift produces an activated form of OsbZIP74 (bZIP74A), which is dependent on OsIRE1. bZIP74A enters nucleus and either directly or indirectly up‐regulates OsNTL3 and other downstream genes. Meanwhile, NTL3P is processed by an unknown mechanism, and the activated OsNTL3 (NTL3A) relocated from plasma membrane to nucleus and up‐regulates OsbZIP74 and other downstream genes. Genetic experiments demonstrate that OsNTL3 is required for thermotolerance in rice. Thus, OsNTL3 relays heat stress signal from ER and plasma membrane to nucleus and regulates heat stress responsive genes in rice.