Under The Condition Of Different Photoperiod And Temperature Rice Flowering Regulation Research

Photoperiod and temperature are two pivotal regulatory factors for plants flowering. The floral transition of plants depends mainly on the accurate measurement of changes of photoperiod and temperature. The flowering time of rice as a facultative short-day (SD) plant is delayed under long-day (LD) condition and/or low temperature condition. To elucidate the regulatory functions of photoperiod and temperature for flowering time, we used Zhonghua11(wild type) and lf1132(mutant) as materials for analyzing the flowering molecular mechanisms under different temperature and photoperiod treatments in this study. We sowed the wide type and the mutant in Hainan (the lower latitude region, N18°15’) and in Tianjin (the higher latitude region, N39°13’) respectively. On the other hand, we used artificial climate cabinets mixing two photoperiods and two temperatures to cultivate the materials, and analyze the interaction between temperature and photoperiod for regulatory flowering time in rice. The photoperiod parameters were:LD,14h light and10h dark; SD,10h light and14h dark. The temperature parameters were:normal temperature,28℃; and low temperature,23℃. The detail results in this study were summarized as follows:1. The mutant is a knock-down of function allele of Hdl gene. The mutant displayed an early heading phenotype, and the growth biomass of the mutant was low, such as its panicle length and plant height. We analyzed the heading-date of the wide type and the mutant in these two different regions, and found that the heading-date of the mutant was earlier than the wild type in either Hainan or Tianjin. And the heading-date of the wide type and the mutant in Tianjin was both delayed compared with Hainan, while the heading-date of the wide type was delayed stronger than the heading-date of the mutant. Photoperiod and temperature results together indicate that the delayed heading-date in Tianjin is mainly caused by LD and lower temperature conditions. The higher latitude region (lower temperature and LD conditions) strongly delays the heading-date of the wild type, which may be due to higher photoperiod sensitivity in the wild type compared with the mutant.2. The Ehdl-Hd3a/RFT1pathway is common to and conserved in both the photoperiodic and temperature flowering regulatory pathways. Expression of Ehdl, Hd3a and RFT1is dramatically reduced at low temperature (23℃), suggesting that suppression of Ehdl, Hd3a and RFT1transcription is an essential cause of delayed flowering under low temperature condition.3. Under LD condition, Ghd7mRNA levels are promoted at low temperature (23℃) compared with normal temperature condition (28℃), suggesting low temperature and LD treatment have a synergistic role in the expression of Ghd7. Therefore, upregulation of Ghd7might be a crucial cause of delayed flowering under low temperature condition.4. Se5and RID1/Ehd2/Osldl do not essentially alter in different temperature treatments, indicating that these genes might act differentiated functions between in photoperiodic regulatory pathway and in temperature regulatory pathway.5. Hdl can negatively regulate Ehdl transcription under LD condition. Hdl can also positively regulate Ghd7transcription under LD condition, suggesting that the heading-date of rice under LD condition is also regulated by the Hdl-Ghd7-Ehdl-RFT1pathway.