NIGT1.4 maintains primary root elongation in response to salt stress through induction of ERF1 in Arabidopsis

Plants employ various molecular mechanisms to maintain primary root elongation upon salt stress. Identification of key functional genes, therein, is important for improving crop salt tolerance. Through analyzing natural variation of the primary root length of Arabidopsis natural population under salt stress, we identified NIGT1.4, encoding an MYB transcription factor, as a novel contributor to maintained root growth under salt stress. Using both T-DNA knockout and functional complementation, NIGT1.4 was confirmed to have a role in promoting primary root growth in response to salt stress. The expression of NIGT1.4 in the root was shown induced by NaCl treatments in an ABA-dependent manner. SnRK2.2 and 2.3 were shown to interact with and phosphorylate NIGT1.4 individually. The growth of the primary root of snrk2.2/2.3/2.6 triple mutant was shown sensitive to salt stress, which was similar to nigt1.4 plants. Using DNA affinity purification sequencing, ERF1, a known positive regulator for primary root elongation and salt tolerance, was identified as a target gene for NIGT1.4. The transcriptional induction of ERF1 by salt stress was shown absent in nigt1.4 background. NIGT1.4 was also confirmed to bind to the promoter region of ERF1 by yeast one-hybrid experiment and to induce the expression of ERF1 by dual-luciferase analysis. All data support the notion that salt- and ABA-elicited NIGT1.4 induces the expression of ERF1 to regulate downstream functional genes that contribute to maintained primary root elongation. NIGT1.4-ERF1, therefore, acts as a signaling node linking regulators for stress resilience and root growth, providing new insights for breeding salt-tolerant crops.