ERD4 proteins, members of the early responsive-to-dehydration family, act as plasma membrane ion channels that contribute to ion homeostasis and modulate plant response to abiotic stresses. However, the functions of ERD4 homologs in non-vascular species remain largely unexplored. Here, we characterized an ERD4 family homolog in Physcomitrium patens (Hedw.) Mitt., PpCSC1 (Calcium-permeable Stress-responsive Cation Channel 1), and investigated its role in salt stress response. PpCSC1 localized to the plasma membrane and functioned as a non-selective cation channel permeable to Na⁺, K⁺, Ca²⁺, and Mg²⁺. Under salt treatment, PpCSC1 transcripts were markedly downregulated, whereas overexpression lines exhibited enhanced salt sensitivity. Ion content analysis further revealed reduced K⁺ accumulation, lowered K⁺/Na⁺ ratios, and elevated Mg²⁺ levels, collectively disrupting ionic homeostasis and impairing salt tolerance. Transcriptional regulation analysis revealed that the C2H2-type zinc finger transcription factor PpSTOP2 directly activated PpCSC1 expression. Notably, PpSTOP2 knockout plants displayed reduced PpCSC1 mRNA accumulation and improved salt tolerance. Together, these findings indicate that PpCSC1 is a plasma membrane-localized cation channel that negatively regulates salt tolerance by disturbing ion balance, and that its regulation by PpSTOP2 integrates upstream signaling with downstream physiological responses. This work provides new insight into how non-selective ion channels shape stress adaptation in early land plants.

Synthetic biology is an interdisciplinary field that applies engineering principles to design and construct novel biological systems or organisms. Initially focused on microbial systems, its applications have expanded to include plants. Plant synthetic biology offers promising solutions to pressing global challenges in agriculture and human health. As a staple crop for much of the world’s population and a model species in plant science, rice has emerged as a pivotal platform in this domain. Significant progress has been achieved in genome engineering through multiplex genome editing, synthetic hybrid rice systems, induction of apomixis, reconstruction of photosynthesis and nitrogen-fixation pathways, and biosynthesis of micronutrients, pharmaceuticals, and therapeutic proteins or peptides. This review summarizes recent advances in rice synthetic biology, outlines current developments, and discusses future research directions.

A rice low temperature-induced albino variant was determined by the recessive ltia1 and ltia2 genes. LTIA1 and LTIA2 encode highly conserved mini-ribonucleases Ⅲ located in chloroplasts and expressed in aerial parts of the plant. At low temperature, LTIA1 and LTIA2 redundantly affect chlorophyll levels, non-photochemical quenching, photosynthetic quantum yield of PS Ⅱ and seedling growth. LTIA1 and LTIA2 proteins are involved in splicing of atpF and the biogenesis of 16S and 23S rRNA in chloroplasts. Presence/absence variation of LTIA1, the ancestral copy, was found only in japonica but that of LTIA2 in all rice subgroups. Accessions with LTIA2 presence tended to be distributed more remote from the equator compared to those with LTIA2 absence. LTIA2 duplicated from LTIA1 at the early stage of divergence of the AA genome Oryza species but deleted againin O. nivara. In cultivated rice, absence of LTIA2 is derived from O. nivara. LTIA1 absence occurred more recently in japonica.