NPR1related

NPR1-related refers to proteins that are homologous to Nonexpressor of Pathogenesis-Related genes 1 (NPR1) and to the NPR1-like gene family in plants. NPR1 itself is a key regulator of systemic acquired resistance (SAR) in flowering plants, mediating the transcriptional activation of pathogenesis-related (PR) genes in response to pathogen attack and salicylic acid (SA). The NPR1-related group includes NPR1 and other NPR1-like proteins such as NPR2, NPR3 and NPR4 in Arabidopsis, and homologs in diverse plant species. The exact number and identity of these family members vary among species, reflecting lineage-specific expansions.

Functionally, NPR1-related proteins act as positive or modulatory regulators of SA signaling and defense gene expression. NPR1 is the canonical coactivator that, upon SA-induced redox changes, translocates from cytoplasm to nucleus and interacts with TGA transcription factors to stimulate PR gene expression. NPR3 and NPR4 function as SA receptors that modulate NPR1 stability via the CUL3 E3 ubiquitin ligase, providing a feedback mechanism that tunes defense responses according to SA levels.

Mechanistically, NPR1 and many of its relatives share structural features such as ankyrin repeat-containing regions that mediate protein–protein interactions, and regulatory domains that control localization, stability, and activity. Redox regulation, protein–protein interactions, and proteasomal turnover are central to NPR1-related signaling.

In research and agriculture, NPR1-related pathways are studied for improving disease resistance and understanding crosstalk between SA signaling and other hormonal pathways. Manipulation of NPR1 or related receptors can influence SAR and PR gene expression, with potential applications in crop protection.