Hd1, Ghd7, and DTH8 synergistically determine the rice heading date and yield-related agronomic traits

Heading date determines the seasonal and regional adaptation of rice(Oryza sativa L.) varieties and is mainly controlled by photoperiod sensitivity(PS). The core heading date genes Hd1, Ghd7, DTH8, and PRR37 act synergistically in regulating the PS. In this study, we systematically analyze the heading date,PS, and agronomic traits of eight homozygous lines with various combinations of Hd1, Ghd7, and DTH8 alleles in the prr37 background under long-day(LD) and short-day(SD) conditions, respectivel...     

Flowering time genes Heading date 1 and Early heading date 1 together control panicle development in rice

Although flowering time is often associated with plant size, little is known about how flowering time genes affect plant architecture. We grew four rice lines having different flowering time genotypes (hd1 ehd1, hd1 Ehd1, Hd1 ehd1 and Hd1 Ehd1) under distinct photoperiod conditions. By using genotype-treatment combinations that resulted in similar flowering times, we were able to compare the effects of flowering time genes on traits related to plant architecture. The results revealed that the combination of Heading-date 1 (Hd1) and Early heading date 1 (Ehd1) can reduce the number of primary branches in a panicle, resulting in smaller spikelet numbers per panicle; this occurs independently of the control of flowering time. In addition, expression of the Hd3a and Rice Flowering-locus T 1 (RFT1) florigen genes was up-regulated in leaves of the Hd1 Ehd1 line at the time of the floral transition. We further revealed that Hd1 and/or Ehd1 caused up-regulation of Terminal Flower 1-like genes and precocious expression of panicle formation-related genes at shoot apical meristems during panicle development. Therefore, two key flowering time genes, Hd1 and Ehd1, can control panicle development in rice; this may affect crop yields in the field through florigen expression in leaf.     

Diversified mechanisms for regulating flowering time in a short-day plant rice

Flowering in rice is influenced by not only endogenous factors that comprise an autonomous pathway, but also environmental effects, such as photoperiod, water availability, and temperature just before floral initiation. Recent molecular genetics studies have elucidated the functional roles of genes involved in the photoperiod pathway, e.g., photoreceptors, circadian clock components, and short-day (SD) promotion factors. Although these molecular players are well conserved between rice andArabidopsis, their actual genetic functions are distinct. This is exemplified byHd1 (aCO counterpart) and phytochromes, in particular, ricePHYA. Hd1 has a dual role in regulating flowering time and the expression ofHd3a (anFT counterpart) repression under long-day (LD) conditions while promotion under SDs. Models have been proposed to explain these photoperiod-dependent antagonistic activities. Some regulatory factors are present in only one of the model systems, e.g.,FLC inArabidopsis orEhd1 in rice. Furthermore, epistatic relationships vary among such flowering regulators asHd3a (FT), OsMADS50 (SOCT), andOsMADS14 (AP1). Further experiments to probe these differences will be essential to enlarging our understanding of the diversified flowering regulation mechanisms in rice.     

水稻开花光周期调控相关基因研究进展

水稻开花调控是一个极其复杂的生命过程,由自身遗传因素和外界环境共同决定。光周期途径是调控水稻开花的关键途径,在这个途径中成花素基因Hd3a和RTF1处于核心地位,其上游调控途径主要包括Hd1依赖途径、Ehd1依赖途径及不依赖于Hd1和Ehd1的途径。这3条途径在汇集了光信号的各种信息后,将信号在Hd3a和RTF1处整合,并通过成花素形式将信息传递给下游开花基因,调控水稻开花。本文从成花素、光信号感受基因和昼夜节律基因、成花素上游调控基因、互作蛋白和下游调控基因等几方面阐述水稻开花光周期调控相关基因的研究现状,为水稻开花调控的深入研究提供参考。     

Comprehensive identification of major flowering time genes and their combinations,which determined rice distribution in Northeast China

Flowering time of rice (Oryza sativa L.) is among the most important agronomic traits for regional adaptation and grain yield. To date, a number of genes or quantitative trait loci (QTLs) controlling flowering time have been identified in rice, and diverse natural allelic variations for these flowering genes have been revealed, which suggested that the underlying regulation mechanism of flowering time in rice is very complicated. Northeast China is a major cultivation region for temperate japonica rice, where the temperature is cooler and the day length is longer. The regional adaptability of local rice cultivar is substantially different from that of other regions. Recently, some flowering genes have been proved to play roles in regulating flowering time of local cultivars. However, a comprehensive analysis of the effectiveness of these flowering genes has not been performed. In the present study, 395 cultivars collected from Northeast China is re-sequenced, SNP and InDel markers were called for 23 selected flowering-related genes. The heading date of these cultivars was also investigated for three consecutive years. Through association analysis, we found that Hd2, Hd4, and Hd5 are major flowering repressors, whereas Dth2 and Hd18 are major flowering promoters. Furthermore, Hd6 and Hd16 were identified as minor flowering repressors, and Hd17 was minor flowering promoter, in that their effectiveness can exclusively be detected when both Hd2 and Hd4 are functional. Collectively, we comprehensively identified the major and minor flowering genes which determine flowering time of temperate japonica rice grown in Northeast China.     

Combinations of Hd2 and Hd4 genes determine rice adaptability to Heilongjiang Province,northern limit of China

Heading date is a key trait in rice domestication and adaption, and a number of quantitative trait loci (QTLs) have been identified. The rice (Oryza sativa L.) cultivars in the Heilongjiang Province, t...