Preferential expression of cell elongation-related genes in leaves of the new elite wheat line Iksan370 with large spikes

The Korean wheat line Iksan370 was recently bred by crossing the paternal line Keumkang with the maternal line Xian83. Iksan370 has a giant phenotype in terms of its whole body architecture, and its height and leaf and spikelet length are higher than those of the paternal line Keumkang. From young seedlings to adult plants, the photosynthetic pigmentation and photosystem II efficiency of Iksan370 and Keumkang lines did not differ significantly; however, Iksan370 lines had significantly larger leaf epidermal cells than Keumkang, resulting in enlarged leaf architecture. Consistently, RNA sequencing analysis and subsequent quantitative real-time PCR analysis indicated that expression of target of rapamycin (TOR) was several fold higher in Iksan370 than in Keumkang, while expression of cell division- and photosynthesis-related genes did not differ among the lines. These data suggest that the giant characteristics of Iksan370 leaves are owing to enhanced expression of TOR, which is involved in cell expansion.