LYSINE KETOGLUTARATE REDUCTASE TRANS-SPLICING RELATED 1 is involved in temperature-dependent root growth in rice.

Root length is one of the important parameters of root traits directly related to uptake of water and nutrients, however, the molecular mechanisms controlling root length are still not fully understood. Here, we isolated a mutant, dice2 (defective in cell elongation 2) of rice (Oryza sativa) showing short roots. The cell length and meristem size of the roots was decreased in the mutant, but the root function in mineral element uptake normalized by root biomass, root cell width and root anatomy was hardly altered compared with the wild-type rice (WT). Intriguingly, the root growth defect in the mutant could be partially rescued by high temperature. The mutant accumulated more H2O2 and glutamic acid, but less O2 •- in the roots at low temperature than WT, but they became similar at high temperature between two lines. A map-based cloning combined with complementation test revealed that the short-root phenotype was caused by a nucleotide substitution of a gene, which was annotated to encode Lysine Ketoglutarate Reductase Trans-Splicing related 1 (OsLKRT1). OsLKRT1 encodes a cytosol-localized protein and was expressed in both the roots and shoots. Furthermore, OsLKRT1 was expressed in all cells of the root tip and root elongation regions. RNA-seq analysis showed that there was no difference in the expression level of genes involved in root development identified so far. These results indicate that the gene identified in this study is involved in novel pathway required for cell elongation of the roots in rice although its exact role remains to be further investigated.