Jokela Venla, Virkajärvi Perttu, Tanskanen Jaakko, Seppänen Mervi M
Department of Agricultural Sciences, University of Helsinki, Box 27, Helsinki, 00014, Finland.
Physiol Plant. 2014 Sep;152(1):152-63. doi: 10.1111/ppl.12141. Epub 2014 Jan 23.
Timothy (Phleum pratense) is a widely grown perennial forage grass in the Nordic region. The canopy consists of three tiller types, of which the stem forming vegetative elongating (ELONG) tiller and generative (GEN) tillers contribute the most to dry matter yield. In this study, the regulation of tiller formation by vernalization, day length (DL) [12 h, short day length (SD); 16 h, long day length (LD)] and gibberellic acid (GA) was investigated in two timothy cultivars. Vernalization resulted in a shift of ELONG to GEN tillers. No vernalization was required for the development of ELONG tillers but SD strictly arrested stem elongation. Vernalization is an important regulator of tiller development but it seemed to be upstream regulated by DL. LD was essential for floral transition and could not be substituted by GA and/or vernalization treatments. Genotypic variation was found in the development of GEN tillers. The ability to produce GEN tillers was associated with significant upregulation of PpVRN3. PpVRN1 expression peaked at the time of vegetative/generative transition, and PpVRN3 after the transfer to LD, suggesting them to have similar functions with cereal vernalization genes. PpVRN1 alone was not sufficient to activate flowering, and upregulation of PpVRN3 possibly together with PpPpd1 was required. Although vernalization downregulated PpMADS10, this gene did not act as a clear flowering repressor. Our results show that flowering signals alter the tiller composition, so they have important effects on yield formation of timothy.
梯牧草（Phleum pratense）是北欧地区广泛种植的多年生饲草。其冠层由三种分蘖类型组成，其中形成茎的营养伸长（ELONG）分蘖和生殖（GEN）分蘖对干物质产量的贡献最大。在本研究中，对两个梯牧草品种进行了研究，探讨了春化处理、日长（DL）[12小时，短日长（SD）；16小时，长日长（LD）]和赤霉素（GA）对分蘖形成的调控作用。春化处理导致ELONG分蘖向GEN分蘖转变。ELONG分蘖的发育不需要春化处理，但短日长会严格抑制茎的伸长。春化处理是分蘖发育的重要调节因子，但它似乎受日长的上游调控。长日长对花的转变至关重要，不能被GA和/或春化处理所替代。在GEN分蘖的发育过程中发现了基因型变异。产生GEN分蘖的能力与PpVRN3的显著上调有关。PpVRN1的表达在营养/生殖转变时达到峰值，PpVRN3在转移到长日长后表达达到峰值，表明它们与禾本科植物的春化基因具有相似的功能。单独的PpVRN1不足以激活开花，可能需要PpVRN3与PpPpd1一起上调。虽然春化处理下调了PpMADS10的表达，但该基因并未表现出明显的开花抑制作用。我们的结果表明，开花信号改变了分蘖组成，因此它们对梯牧草的产量形成具有重要影响。
