ABSTRACT: Reticulon family proteins are membrane-spanning proteins localized in the endoplasmic reticulum (ER) and are present in all eukaryotes. In animal cells, these proteins, known as reticulons, have a wide range of functions. These functions encompass involvement in vesicle formation, ER membrane morphogenesis, and the inhibition of nerve regeneration. Conversely, in plants, our understanding of the function of reticulon-like family proteins (RTNLBs) remains limited. In the plant Arabidopsis, the RTBLB gene family comprises twenty-one members, with RTNLB16 being the most intricate. The AtRTNLB16 gene consists of seven splice variants, each encoding seven distinct protein isoforms. An Arabidopsis T-DNA mutant (Salk_122275/rtnlb16-1), which is a knockout for the upper coding frame isoform 7 while concurrently overexpressing the other isoforms through the CaMV 35S promoter at the left border of the T-DNA insertion, exhibits growth retardation, reduced chlorophyll levels, and insensitivity to abscisic acid or senescence stimuli. Under a diurnal regime of 16 hours of light followed by 8 hours of darkness, which activates the 35S promoter, the expression of RTNLB16 transcripts in the rtnlb16-1 mutant intensifies, resulting in profound growth inhibition. Conversely, growing under a continuous low-light (CLL) condition curbs the overexpression and mitigates this phenotype. Under a diurnal regime of 16 hours of light followed by 8 hours of darkness, which activates the 35S promoter, the expression of RTNLB16 transcripts in the rtnlb16-1 mutant intensifies, resulting in profound growth inhibition. Conversely, growing under a continuous low-light (CLL) condition curbs the overexpression and mitigates this phenotype. We utilized the altered expression of the RTLB16 gene in this mutant line due to its dependence on the light regime. Our aim was to uncover the biological processes in which it participates. To achieve this, we conducted RNA sequencing on leaves from four-week-old wild-type (Col-0) and rtnlb16-1 plants grown under CLL or 16:8 light regimes.
