Unveiling the wheat NTP gene family: insights from genome-wide identification and TaNTP6 haplotype analysis

Nucleotidyl transferase proteins (NTPs) regulate RNA homeostasis by mediating templated-independent nucleotide additions to RNA termini, thereby being implicated in crucial roles during plant growth, development, and stress responses. However, investigations of the NTP gene family have been limited to few plants, with NTP genes in wheat remaining uncharacterized.

In this study, we identified 34 TaNTP genes in wheat and classified them into three phylogenetic groups (G1-G3). All 20 segmental duplication events occurred specifically in G3. G3 TaNTPs contain unique motifs, while G1 members possess an extra PAP association domain absent in G2 and G3. Protein interaction networks also supported group divergence, with G1 and G3 proteins forming separate modules (Module Ⅰ and Ⅱ), and G2 distributed across both, suggesting functional specialization or dual roles. Expression profiling revealed that most TaNTPs are lowly expressed in leaves but upregulated under heat-drought stress. Many are also responsive to salt, ABA, and SA, supporting roles in stress adaptation. Notably, TaNTP6A/B/D show high expression levels in grains, and the different haplotypes of TaNTP6A/B/D are significantly correlated with thousand kernel weight (TKW), implying TaNTP6A/B/D are crucial regulators for grain development. Among them, TaNTP6A-Hap1, TaNTP6B-Hap2, and TaNTP6D-Hap5/6 can be regarded as elite haplotypes favorable for grain yield. Additionally, subcellular localization analysis revealed that TaNTP4A and TaNTP1A, the orthologs of AtHESO1 and AtURT1, were detected to be mainly located in the cell nuclear.

These results provide pivotal insights into the NTP family in wheat. Importantly, the identification of elite TaNTP6A/B/D haplotypes offers valuable genetic resources for facilitating high-yield wheat breeding programs.