Expression of AtNF-YB1 in rice leading to early flowering shows potential in rice breeding

Abstract

Grain yield and growth period are two critical agronomic traits for a rice cultivar to be used in field production. The growth period is mainly determined by the flowering time, which also greatly affects grain yields. An Arabidopsis gene, AtNF-YB1, was introduced into rice, including inbred Kasalath and two hybrids, Jinfeng × Chenghui 727 and Jinfeng × Chuanhui 907. All the transgenic rice showed flowering early under both natural long-day (NLD) and natural short-day (NSD). Kasalath with expression of the gene also showed shorter plant height and less grain yield with the decrease in spike length and grain number but more productive panicles. But, for the hybrids, much smaller or even no reduction of spike length, grain number, and more productive panicle were observed so that grain yields were kept or even increased underNLD. Transcript analysis of the major flowering-time genes suggested that suppression of the Ghd7 transcription activated flowering transition early in the transgenic rice. RNA-Seq further demonstrated that three pathways related to plant photosynthesis were markedly up-regulated in both Jinfeng B and hybrid Jinfeng ×Chuanhui 907. Accordingly, up-regulated photosynthetic rates in the transgenic plants were then observed in the subsequent experiments. All these results suggest that expression of AtNF-YB1 in rice may be useful for creating variety with early ripening, particularly for hybrid rice.