SNc Nuclease Genes AtCAN1 and AtCAN2 Are Expressed in Programmed Cell Death and Endoreduplicating Tissues in...

Controlled degradation of genomic DNA is a hallmark of programmed cell death (PCD) in plants and animals. In plants, nucleic acid degradation during PCD enables nutrient redistribution. S1/P1 nucleases are established participants; however, the staphylococcal-like (SNc) nucleases, represented in Arabidopsis thaliana by plasma membrane-localized AtCAN1 and AtCAN2, have not been characterized in this context. Using promoter-driven GUS reporter assays, we show that AtCAN1, and to a lesser extent AtCAN2, are expressed in three tissue categories: (i) tissues described in the scientific literature as classical examples of PCD-associated structures; (ii) cells at the plant-environment interface susceptible to pathogen attack, root hairs, guard cells, and hydathodes; and (iii) endoreduplicated structures: stipules, trichomes, and basal hypocotyl. Expression patterns were independently confirmed using publicly available microarray and RNA-seq datasets. Loss of AtCAN1 function reduces rosette growth. AtCAN1 is highly tissue-specific; AtCAN2 shows a broader, weaker pattern, consistent with subfunctionalization. Overlapping expression with S1/P1 nucleases in PCD tissues suggests complementary nucleolytic roles. Unlike S1/P1 nucleases, which are nuclear, SNc nucleases localize to the plasma membrane, implying distinct yet cooperative pathways. The expression of SNc nucleases in endoreduplicating organs suggests their potential involvement in an unidentified process of polyploid DNA recycling.