Differentially expressed microRNAs between WT and AtC3H3 OX, and WT and AtC3H26 OX

CCCH-type zinc finger (ZF) proteins comprise a diverse family of RNA- and DNA-binding regulators that play crucial roles in plant growth, development, and responses to stress. While tandem CCCH zinc finger (TZF) proteins have been extensively studied, the molecular functions of non-TZF members remain less understood. Here, we characterized Arabidopsis thaliana AtC3H26, a non-TZF CCCH protein and paralog of AtC3H3, and demonstrated its role as a ribonuclease (RNase) in salt stress tolerance and phosphate (Pi) homeostasis. In vitro assays confirmed that AtC3H26 degrades RNA substrates in a dose-dependent manner. mRNA sequencing of OX lines revealed a significant upregulation of phosphate starvation–responsive genes, including SPX1, PS2/PECP2, and SRG3/GDPD1, whereas small RNA sequencing identified the downregulation of miR399 and miR827, which are involved in the Pi starvation response. AtC3H26 OX plants accumulated higher Pi levels than wild type, suggesting that AtC3H26 modulates Pi accumulation. Collectively, these findings establish AtC3H26 as a novel cytoplasmic RNase that coordinates RNA turnover with stress and nutrient signaling in Arabidopsis. Overall design: Differential gene expression between WT and AtC3H3 OX, as well as between WT and AtC3H26 OX, was examined at 10 days after germination under SD conditions (8-hour-light and 16-hour-dark cycle) on a microRNA level.