Wheat SHORT ROOT LENGTH 1 Gene TaSRL1 Regulates Root Length In An Auxin-dependent Pathway

Root is the unique organ of water and nutrients uptake and sensing environmental stimulus in the soil.The optimization of root system architecture contributes to the stress tolerance and yield improvement.With the shortage of water resources and the environmental problems caused by the fertilizer usage,a green revolution that does not rely on expensive inputs is needed.People have turned their attention to the research of the root system,the main organ delivering water and nutrients in plants.We cloned a novel ERF transcription factor gene TaSRL1(SHORT ROOT LENGTH 1)from wheat(Triticum aestivum).ERFs(Ethylene response factors)belong to the AP2(APETALA2)superfamily.Research show that ERFs widely participate in multiple abiotic stress tolerance and root development.To clarify the effects of TaSRL1 on plant growth and development,the CDS of TaSRL1 was cloned into p CUbi1390 vector to generate overexpression transgenic rice.We identified that TaSRL1 integrates auxin and JA signaling to regulate root elongation.Moreover,it is associated with root depth and angle,plant height and 1000-grain weight.The functional marker developed here will be helpful for the improvement of root system,plant architecture and yield during the wheat breeding process.The main results were as follows.1.The coding sequence lengths of TaSRL1-4A,TaSRL1-4B and TaSRL1-4D are 1021 bp,1073 bp and 1058 bp,respectively.All the three genomic sequences of TaSRL1 s only contain an intron.The amino acids sequence similarity of TaSRL1-4A and TaSRL1-4B is 86.79%,89.91% between TaSRL1-4A and TaSRL1-4D,and 86.08% between TaSRL1-4B and TaSRL1-4D.Neighbor-joining phylogenetic tree indicates that TaSRL1 s are highly conservative in monocotyledon.2.The temporal and spatial expression pattern show that TaSRL1 is mainly expressed in root at the seedling stage and jointing stage.The expression of TaSRL1 is down-regulated after treatment of 1 n M NAA which promotes the growth of wheat roots,but up-regulated after treatment of 0.1 μM NAA which inhibits root growth.The precise regulation of expression level by auxin suggest that TaSRL1 may play roles in the auxin-dependent root growth.In addition,the expression of TaSRL1 is inhibited by ABA and Me JA,but up-regulated by PEG,indicating that TaSRL1 may be involved in the Me JA and ABA signaling pathways,and drought stress responses.3.Subcellular localization indicates that TaSRL1 is a nuclear protein and the amino acids from 234 to 268 aa are crucial for transcription activation.4.The TaSRL1 overexpression rice lines exhibited shorter root than wild type Kitaake at both seedling and booting stages.5.The q RT-PCR results show that TaSRL1 regulated expression of genes related to auxin synthesis,transport and signaling.6.The interaction of TaSRL1 and TIFY9 is verified by yeast two-hybrid assay,luciferase complementation imaging assay and bimolecular fluorescence complementation assay.7.Further studies revealed that TaSRL1 induced expression of the auxin transport gene Ta PIN2 by directly binding to its promoter,while the interaction of TaSRL1 and Ta TIFY9 repressed Ta PIN2 expression.8.The sequence polymorphisms in the coding sequences of TaSRL1-4A,-4B and-4D,and flanking regions in 32 hexaploid accessions with high variation were analyzed.Three SNPs were detected in TaSRL1-4A,and no polymorphism in TaSRL1-4B and TaSRL1-4D.According to SNP-96(T/C),a d CAPs marker TaSRL1-4A-d CAPs was designed.Association analysis showed that TaSRL1-4A was associated with root depth and angle,plant height and 1000-grain weight of wheat.9.We investigated the frequency of the two haplotypes in 157 landraces,and 348 modern cultivars,and the distribution in Chinese wheat production zones.The results suggested that the haplotype Hap-4A-2 with shallow roots,short plant height and high 1000-grain weight has been positively selected in Chinese wheat breeding history.