The Wheat SHORT ROOT LENGTH 1 Gene TaSRL1 Controls Root Length in an Auxin-Dependent Pathway

The root is the main organ for water and nutrient uptake and sensing environmental stimuli in the soil. The optimization of root system architecture contributes to stress tolerance and yield improvement. ERF (ETHYLENE RESPONSIVE FACTOR) is one of the plant-specific transcription factor families associated with various developmental processes and stress tolerance. We cloned a novel ERF transcription factor gene TaSRL1 (SHORT ROOT LENGTH 1) from wheat (Triticum aestivum) which is mainly expressed in root. Ectopic expression of TaSRL1 in rice resulted in short root length and plant height. TaSRL1 regulated expression of genes related to auxin synthesis, transport, and signaling. Further studies revealed that TaSRL1 induced expression of the auxin transport gene TaPIN2 by directly binding to its promoter, while the interaction of TaSRL1 and TaTIFY9 repressed TaPIN2 expression. Sequence polymorphisms and association analysis showed that TaSRL1-4A was associated with root depth and angle, plant height, and 1000-grain weight of wheat. The haplotype Hap-4A-2 with shallow roots, short plant height, and high 1000-grain weight has been positively selected in the Chinese wheat breeding process. We demonstrated that TaSRL1 functions as a direct regulator of TaPIN2 in the auxin-dependent pathway, and integrates auxin and jasmonate signaling by interacting with TaTIFY9 to repress root growth. Furthermore, the molecular marker of TaSRL1-4A is valuable for the improvement of the root system, plant architecture, and yield in the wheat breeding process.