Polyploidized Rice Improves Plant Height and Yield through Regulating Expression of Yield Related Genes.
Polyploidization is one of the effective ways to improve plant height and yield of rice (Oryza sativa L.). However, the molecular mechanism of regulation is not yet fully understood. Here, we investigated the agronomic traits of diploid (Balilla-2x) and tetraploid (Balilla-4x) of japonica rice variety Balilla. Compared with Balilla-2x, Balilla-4x exhibited significantly increased plant height, spike length and yield per plant. RNA-seq analysis of  the leaves of  Balilla-2x and Balilla-4x was performed and the results showed that the expression levels of yield related genes (e.g., STH1, OsYUC9, and OsDEP1) were significantly upregulated in Balilla-4x rice plants, these genes are related to plant height and panicle development. These results indicated that polyploidization changed the expression of genes related to agronomic traits such as plant height and spike length, thereby increasing rice yield. This study provides a further basis for understanding the yield of rice after polyploidization, and can serve as a new theoretical reference for breeding high-yielding rice varieties achieved. Overall design: Balilla-2x (O. sativa ssp. japonica, 2n = 2x = 24) is a low seed setting rate rice variety from Italy, and the artificially synthesized tetraploid ('Balilla-4x', 2n = 4x = 48) is a doubling of 'Balilla' diploid (Balilla-2x).  The rice plants (Balilla-2x and Balilla-4x) used in this study, grew in the paddy field of experimental fields in Shanghai during the natural growing seasons, and the leaves were sampled for RNA-seq analysis.