Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410082, People's Republic of China.
National Key Facility for Crop Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing, 100081, People's Republic of China.
Plant Mol Biol. 2016 Sep;92(1-2):209-22. doi: 10.1007/s11103-016-0506-3. Epub 2016 Jul 12.
Flowering time determines the adaptability of crop plants to different local environments, thus being one of the most important agronomic traits targeted in breeding programs. Photoperiod is one of the key factors that control flowering in plant. A number of genes that participate in the photoperiod pathway have been characterized in long-day plants such as Arabidopsis, as well as in short-day plants such as Oryza sativa. Of those, CONSTANS (CO) as a floral integrator promotes flowering in Arabidopsis under long day conditions. In rice, Heading date1 (Hd1), a homologue of CO, functions in an opposite way, which inhibits flowering under long day conditions and induces flowering under short day conditions. Here, we show that another CONSTANS-like (COL) gene, OsCOL13, negatively regulates flowering in rice under both long and short day conditions. Overexpression of OsCOL13 delays flowering regardless of day length. We also demonstrated that OsCOL13 has a constitutive and rhythmic expression pattern, and that OsCOL13 is localized to the nucleus. OsCOL13 displays transcriptional activation activity in the yeast assays and likely forms homodimers in vivo. OsCOL13 suppresses the florigen genes Hd3a and RFT1 by repressing Ehd1, but has no relationship with other known Ehd1 regulators as determined by using mutants or near isogenic lines. In addition, the transcriptional level of OsCOL13 significantly decreased in the osphyb mutant, but remained unchanged in the osphya and osphyc mutants. Thus, we conclude that OsCOL13 functions as a negative regulator downstream of OsphyB and upstream of Ehd1 in the photoperiodic flowering in rice.
开花时间决定了作物对不同当地环境的适应性，因此成为了育种计划中最重要的农艺性状之一。光周期是控制植物开花的关键因素之一。许多参与光周期途径的基因已在长日照植物（如拟南芥）和短日照植物（如水稻）中得到了鉴定。其中，CONSTANS（CO）作为花的整合因子，在长日照条件下促进拟南芥开花。在水稻中，与 CO 同源的Heading date1（Hd1），其作用方式相反，在长日照条件下抑制开花，在短日照条件下诱导开花。在这里，我们表明另一个类似 CONSTANS（COL）的基因 OsCOL13 在长日照和短日照条件下均负调控水稻开花。过表达 OsCOL13 会延迟开花，而不论日照长度如何。我们还证明了 OsCOL13 具有组成型和节律性的表达模式，并且 OsCOL13 定位于细胞核中。OsCOL13 在酵母测定中显示出转录激活活性，并且可能在体内形成同源二聚体。OsCOL13 通过抑制 Ehd1 来抑制开花基因 Hd3a 和 RFT1，但与其他已知的 Ehd1 调节剂没有关系，这是通过使用突变体或近等基因系确定的。此外，在 osphyb 突变体中，OsCOL13 的转录水平显著降低，但在 osphya 和 osphyc 突变体中保持不变。因此，我们得出结论，OsCOL13 作为 OsphyB 的下游和 Ehd1 的上游在水稻光周期开花中作为负调控因子发挥作用。
