The in the Promoter Is Important but Not Essential for Infection Thread Formation During Rhizobia Symbiosis.

The establishment of the legume-rhizobia symbiosis, termed the root-nodule symbiosis (RNS), requires elaborate interactions at the molecular level. The host plant-derived transcription factor NODULE INCEPTION (NIN) is known to be crucial for RNS, regulating associated processes such as alteration of root hair morphology, infection thread formation, and cell division during nodulation. This emphasizes the importance of the precise spatiotemporal regulation of expression for the establishment of RNS; however, the detailed role of promoter sequences in this process remains unclear. The mutant, a mutant allele containing a chromosomal translocation approximately 7 kb upstream of the start codon, does not form nodules but does form infection threads, indicating that the region within 7 kb of the start codon contributes to expression during infection thread formation. CYCLOPS binds to a CYCLOPS response element () in the promoter, and mutants are defective in infection thread formation. Here, we performed complementation analysis in mutants, using various truncated forms of the promoter, and found that the is important for infection thread formation. Additionally, the deletion mutant, generated through CRISPR/Cas9 technology, displayed a significant reduction in infection thread formation, indicating that the is important for the fine-tuning of expression during this process. However, the fact that infection thread formation is not completely abolished in the deletion mutant suggests that and factors other than CYCLOPS and the may cooperatively regulate expression for the induction of infection thread formation. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.