Expression profiles and regulation of FT/TFL1-like genes in Pinus tabuliformis
目的PEBP基因家族的FT-like与TFL1-like亚基因家族在被子植物生殖发育调控网络中处于核心调控节点，而在针叶树中，仅存在未分化的FT/TFL1-like亚基因家族。研究表明针叶树FT/TFL1-like可能在生殖发育、生长节律及休眠过程中发挥重要功能。然而，目前关于针叶树FT/TFL1-like基因系统的表达模式与不同环境因子对其表达的调控仍然缺乏深入认识。 方法本研究从油松中分离得到两个FT/TFL1-like基因，分别命名为PtTFL1与PtTFL2，对它们在不同组织、不同发育阶段雌雄球花、休眠与解除休眠过程中针叶、深冬相对高温、不同光质与光周期处理中的表达水平进行了系统分析。 结果PtTFL1仅在花粉中特异表达，在其他组织中只有痕量表达或不表达。而PtTFL2表达范围非常广泛，且在芽组织中的表达丰度显著高于其他组织，二者在快速增殖的愈伤组织中均无明显表达；另外，对PtTFL2在不同环境下表达水平进行分析发现，PtTFL2在芽、针叶休眠时期大量积累，且随着休眠解除表达量水平持续降低；在不足以打破休眠的相对高温处理下，PtTFL2的表达受到极显著的抑制；短日照下远红光处理可以高效诱导PtTFL2的表达。 结论由此可知，PtTFL1在油松生殖发育进程中的特异性可能与花粉成熟过程相关，而PtTFL2可能参与更多其他发育调控，但二者均不是维持细胞活性所必须的基因；秋季环境条件非常利于PtTFL2在针叶、芽中大量表达，其表达模式与休眠过程高度相关，但PtTFL2对温度响应过于敏感，其在针叶、雌雄球花中的表达模式很可能是对温度响应的结果，这表明PtTFL2自身的表达可能并不足以维持休眠，也并不作为球花发育调控中的控制因子，而很可能只是作为一个温度、短日照远红光信号的感受与传递因子。本研究为深入理解FT/TFL1-like基因在油松生殖与休眠等重要发育过程中的功能，揭示不同环境因子对其表达的调控作用提供了重要依据。Abstract: ObjectiveThere are three subfamilies of the PEBP gene family:FT-like, TFL1-like and FT/TFL11-like. We have known that FT/TFL1-like genes are the core regulation hubs in reproductive regulation network in angiosperms. Only the undifferentiated FT/TFL1-like subfamily in conifers was suggested play important roles of reproduction, growth rhythm and dormancy process. However, the knowledge of its expression profiles and the expressional regulation by different environmental factors about the FT/TFL1-like genes in conifers are still limited. This may result in some inaccurate speculation about the role of its related expression mechanism. MethodIn this study, we isolated two FT/TFL1-like genes form Chinese pine (Pinus tabuliformis), named as PtTFL1 and PtTFL2. The expression level of these genes in different tissues, the developing male cones and female cones in different stage, the needles during the dormancy and dormancy release, the response to relative warmer temperature and under different day length and light were studied. ResultThe results showed that PtTFL1 was specifically expressed in pollen and nearly no expression in other tissues. But the PtTFL2 was very broadly expressed and significantly expressed in the bud tissue than other tissues. But both of two genes were not significantly expressed in the rapidly proliferating callus; in addition, the analysis of the expression level of PtTFL2 in different environments was found. PtTFL2 accumulated in buds and conifers during the dormancy period and decreased when dormancy release; under the condition of relatively high temperature but not enough to break dormancy, the expression of PtTFL2 was significantly inhibited, which was similar to that of far red light treatment. ConclusionIt can be seen that PtTFL1 may be related to pollen maturation process in the reproductive development process of Pinus tabuliformis, but PtTFL2 may be involved in more other developmental regulation, both of them are not necessary to maintain cell activity. The autumn environmental conditions are very conducive to the accumulation of PtTFL2 in male, female cones and needle, this expression profile of it is highly correlated with dormancy. However, PtTFL2 expression pattern is too sensitive to temperature and the expression patterns of male, female cones and needles are more likely to result in response to temperature, indicating that PtTFL2 itself probably is only a temperature response and signal transmission factor and regulated by far-red light under short day rather than related to the regulation of cone development or be sufficient to maintain dormancy. This study provides important data for further understanding the function of FT/TFL1-like gene in important developmental processes, such as reproductive and dormancy of Chinese pine, and its expression regulation by different environmental factors.
图 1 种子植物FT/TFL1-like蛋白系统发育分析
Figure 1. Phylogenetic analysis of seed plant FT/TFL1-like protein
The figures show an unrooted maximum likelihood tree based on the amino acid sequence. The amino acid name and ID were provided on right of each branch. The horizontal branch lengths are proportional to the estimated number of amino acid substitutions per residue. The arrows indicate the proteins encoded by P. tabuliformis genes investigated in this study.(Ptrichocarpa, Populus trichocarpa; Athaliana, Arabidopsis thaliana; Vvinifera, Vitis vinifera; Osativa, Oryza sativa; Pabies, Picea abies; Pglauca, Picea glauca; Ptabuliformis, Pinus tabuliformis; Psitchensis, Picea sitchensis; Pcontorta, Pinus contorta).
图 4 油松PtTFL2在雌雄球花发育中的表达模式
3个生物学重复；VB代表叶芽；M1代表幼年雄球花；M2~M6代表 5个不同时期的雄球花；F1代表幼年雌球花；F2~F6代表 5个不同时期的雌球花。
Figure 4. Expression patterns of PtTFL2 in developing male and female cones of P. tabuliformis
Three biological repeats; VB represents vegetative bud; M1 represents juvenile male cone; M2-M6 represent five different development stages of male cone; F1 represents juvenile female cone; F2-F6 represent five different development stages of female cone.
图 7 长日照、短日照、红光与远红光对PtTFL2的表达调控
Figure 7. Expressional regulation of PtTFL2 by the day length, red light and far-red light
Three biological repeats; LB is long bright light; LF is long far-red light; LR is long red light; SB is short bright light; SF is short far-red light; SR is short red light.
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