Enhanced JAGN1 expression Modulates ER Stress Signaling and Promotes Survival in IRE1-Deficient Arabidopsis

Jagunal homolog 1 (JAGN1) is essential for endoplasmic reticulum (ER) organization and function in animals, where mutations cause severe congenital neutropenia in humans. Although JAGN1 function is conserved across animal species, its role in plants has not been examined. Here, we investigated JAGN1 function in Arabidopsis using a transgenic line with elevated JAGN1 expression exposed to ER stress inducers. Increased JAGN1 expression in Inositol Requiring Enzyme 1 (ire1) double knockout plants partially restored survivability under ER stress and enhanced expression of unfolded protein response (UPR) genes, including BiP3 , PDI9 , and SAR1a , indicating an IRE1-independent mechanism. In contrast, crossing the JAGN1 overexpression line with Basic Leucine Zipper 28 ( bZIP28 ) mutants reduced survival and failed to alter downstream gene expression. These results provide the first evidence that JAGN1 function is conserved across plant and animal kingdoms and establish Arabidopsis as a model system to study JAGN1 biology and disease-associated mutations.