Milhinhos Ana, Bollhöner Benjamin, Blazquez Miguel A, Novák Ondřej, Miguel Célia M, Tuominen Hannele
Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Umeå, Sweden.
Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas - Universidad Politécnica de Valencia, Valencia, Spain.
Front Plant Sci. 2020 Nov 16;11:601858. doi: 10.3389/fpls.2020.601858. eCollection 2020.
In the primary root and young hypocotyl of , ACAULIS5 promotes translation of SUPPRESSOR OF ACAULIS51 (SAC51) and thereby inhibits cytokinin biosynthesis and vascular cell division. In this study, the relationships between ACAULIS5, SAC51 and cytokinin biosynthesis were investigated during secondary growth of stems. Overexpression of from the constitutive promoter in hybrid aspen ( × ) trees suppressed the expression level of , which resulted in low levels of the physiologically active cytokinin bases as well as their direct riboside precursors in the transgenic lines. Low expression and low cytokinin levels of the transgenic trees coincided with low cambial activity of the stem. ACAULIS5 therefore, contrary to its function in young seedlings in , stimulates cytokinin accumulation and cambial activity during secondary growth of the stem. This function is not derived from maturing secondary xylem tissues as transgenic suppression of levels in these tissues did not influence secondary growth. Interestingly, evidence was obtained for increased activity of the anticlinal division of the cambial initials under conditions of low expression and low cytokinin accumulation. We propose that ACAULIS5 integrates auxin and cytokinin signaling to promote extensive secondary growth of tree stems.
在[植物名称]的初生根和幼胚轴中，ACAULIS5促进ACAULIS51抑制因子（SAC51）的翻译，从而抑制细胞分裂素生物合成和维管细胞分裂。在本研究中，研究了茎的次生生长过程中ACAULIS5、SAC51与细胞分裂素生物合成之间的关系。在杂交杨树（×）中由组成型[启动子名称]启动子过表达[基因名称]抑制了[基因名称]的表达水平，这导致转基因株系中生理活性细胞分裂素碱基及其直接核苷前体水平较低。转基因树的低[基因名称]表达和低细胞分裂素水平与茎的形成层低活性一致。因此，与它在[植物名称]幼苗中的功能相反，ACAULIS5在茎的次生生长过程中刺激细胞分裂素积累和形成层活性。这种功能并非源于成熟的次生木质部组织，因为在这些组织中转基因抑制[基因名称]水平并未影响次生生长。有趣的是，在低[基因名称]表达和低细胞分裂素积累条件下，获得了形成层原始细胞垂周分裂活性增加的证据。我们提出，ACAULIS5整合生长素和细胞分裂素信号传导以促进树木茎的广泛次生生长。
