Transcriptomic Analysis Reveals the Contribution of QMrl-7B to Wheat Root Growth and Development
Abstract Backgound: Roots are the major organs for water and nutrient acquisition and substantially affect plant growth, development and reproduction. Improvements to root system architecture are highly important for increasing yield potential of bread wheat. QMrl-7B, a major stable quantitative trait locus (QTL) that controls maximum root length (MRL), strongly contributes to an improved root system in wheat. Results: To further analyse the biological functions of QMrl-7B in root development, two types of Triticum aestivum near isogenic lines (NILs), one with superior QMrl-7B alleles from cultivar Kenong 9204 (KN9204) and another with inferior QMrl-7B alleles from cultivar Jing 411 (J411), were subjected to transcriptomic analysis. Among all the mapped genes analysed, 4871 genes were identified as being differentially expressed between the pairwise NILs under different nitrogen (N) conditions, with 3543 genes expressed under normal-nitrogen (NN) condition and 2689 genes expressed under low-nitrogen (LN) condition. These genes encode proteins that include mainly NO3- transporters, phytohormone signalling components and transcription factors (TFs), indicating the presence of a complex regulatory network involved in root determination. In addition, among the 13524 LN-induced differentially expressed genes (DEGs) detected in this assay, 4308 were specifically expressed in the A-NIL which brings superior alleles, and 2463 were expressed specifically in the B-NIL which brings inferior alleles. These DEGs reflect different responses of the two types of NILs to varying N supplies, which likely involve LN-induced root growth. Conclusions: These results explain the better-developed root system and increased root vitality provided by the superior alleles of QMrl-7B and provide a deeper understanding of the genetic underpinnings of root traits, pointing to a valuable locus suitable for future breeding efforts for sustainable agriculture.