Division of Biochemistry, Department of Biology, Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstrasse 5, 91058 Erlangen, Germany.
Cell and Molecular Sciences, The James Hutton Institute, Invergowrie, Dundee DD2 5DA, Scotland, UK.
Curr Biol. 2019 May 20;29(10):1614-1624.e3. doi: 10.1016/j.cub.2019.04.027. Epub 2019 May 2.
Understanding tuberization in the major crop plant potato (Solanum tuberosum L.) is of importance to secure yield even under changing environmental conditions. Tuber formation is controlled by a homolog of the floral inductor FLOWERING LOCUS T, referred to as SP6A. To gain deeper insights into its function, we created transgenic potato plants overexpressing a codon-optimized version of SP6A, SP6A, to avoid silencing effects. These plants exhibited extremely early tuberization at the juvenile stage, hindering green biomass development and indicating a tremendous shift in the source sink balance. The meristem identity was altered in dormant buds of transgenic tubers. This strong phenotype, not being reported so far for plants overexpressing an unmodified SP6A, could be due to post-transcriptional regulation. In fact, a putative SP6A-specific small regulatory RNA was identified in potato. It was effectively repressing SP6A mRNA accumulation in transient assays as well as in leaves of young potato plants prior to tuber formation. SP6A expression is downregulated under heat, preventing tuberization. The molecular mechanism has not been elucidated yet. We showed that this small RNA is strongly upregulated under heat. The importance of the small RNA was demonstrated by overexpression of a target mimicry construct, which led to an increased SP6A expression, enabling tuberization even under continuous heat conditions, which abolished tuber formation in the wild-type. Thus, our study describes an additional regulatory mechanism for SP6A besides the well-known pathway that integrates both developmental and environmental signals to control tuberization and is therefore a promising target for breeding of heat-tolerant potato.
了解主要作物马铃薯（Solanum tuberosum L.）的块茎形成对于在不断变化的环境条件下确保产量至关重要。块茎形成受花诱导因子 FLOWERING LOCUS T 的同源物控制，称为 SP6A。为了更深入地了解其功能，我们创建了过表达优化密码子版本 SP6A（SP6A）的转基因马铃薯植物，以避免沉默效应。这些植物在幼年期表现出极早的块茎形成，阻碍了绿色生物量的发育，并表明源库平衡发生了巨大变化。休眠芽中的分生组织身份发生了改变。这种强烈的表型在目前为止过表达未修饰的 SP6A 的植物中尚未报道过，可能是由于转录后调控。事实上，在马铃薯中鉴定出了一种假定的 SP6A 特异性小调节 RNA。它在瞬时测定以及块茎形成之前的年轻马铃薯植物的叶片中有效地抑制了 SP6A mRNA 的积累。SP6A 的表达在高温下被下调，从而阻止了块茎形成。目前尚未阐明其分子机制。我们表明，这种小 RNA 在高温下强烈上调。通过过表达靶 mimicry 构建体证明了该小 RNA 的重要性，这导致 SP6A 表达增加，即使在持续高温条件下也能进行块茎形成，而在野生型中则会消除块茎形成。因此，我们的研究描述了除了众所周知的途径之外，SP6A 的另一种调控机制，该途径整合了发育和环境信号来控制块茎形成，因此是培育耐热马铃薯的有前途的目标。
