Untranslated Regions of a Mobile Transcript Mediate RNA Metabolism

Abstract

BEL1-like transcription factors are ubiquitous in plants and interact with KNOTTED1 types to regulate numerous developmental processes. In potato (Solanum tuberosum subsp. andigena), the BEL1-like transcription factor StBEL5 and its Knox protein partner regulate tuber formation by targeting genes that control growth. RNA detection methods and heterografting experiments demonstrated that StBEL5 transcripts are present in phloem cells and move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA originates in leaf veins and petioles and is induced by a shortday photoperiod, regulated by the untranslated regions, and correlated with enhanced tuber production. Assays for RNA mobility suggest that both 5# and 3# untranslated regions contribute to the preferential accumulation of the StBEL5 RNA but that the 3# untranslated region may contribute more to transport from the leaf to the stem and into the stolons. Addition of the StBEL5 untranslated regions to another BEL1-like mRNA resulted in its preferential transport to stolon tips and enhanced tuber production. Transcript stability assays showed that the untranslated regions and a long-day photoperiod enhanced StBEL5 RNA stability in shoot tips. Upon fusion of the untranslated regions of StBEL5 to a b-glucuronidase marker, translation in tobacco (Nicotiana tabacum) protoplasts was repressed by those constructs containing the 3# untranslated sequence. These results demonstrate that the untranslated regions of the mRNA of StBEL5 are involved in mediating its long-distance transport, in maintaining transcript stability, and in controlling translation.

The Multiple Signals That Control Tuber Formation

“…In this way, the movement of StBEL5 RNA is induced by SD and the presence of its 39 UTR. Long-distance transport of StBEL5 mRNA has been verified using RNA movement assays in both whole plants and heterografts (Banerjee et al, 2006(Banerjee et al, , 2009Lin et al, 2013;Cho et al, 2015). Movement through the phloem also has been confirmed for a BEL5-like transcript in Arabidopsis (Notaguchi et al, 2015).…”

“…There are numerous documented examples of StBEL5's effect on tuberization in both a commercial cultivar and the photoperiod-responsive subspecies andigena (Chen et al, 2003;Banerjee et al, 2006Banerjee et al, , 2009Cho et al, 2015). Overexpression and enhanced accumulation led to early, increased tuberization, whereas RNA interference suppression of StBEL5 significantly reduced tuber yields in several independent lines (Sharma et al, 2016).…”

Transcript Abundance Explains mRNA Mobility Data in Arabidopsis thaliana

“…The consistency of the abundance model with existing experimental data does not imply that identified mobile mRNA species are not biologically relevant signaling molecules. The probability of reaching the cell surface itself could be a biologically relevant and regulated mechanism, in which the balance between half-life and transcription rate determines the mobility of mRNA species; indeed, mRNA 59 and 39 untranslated regions associated with increased mobility have been shown to increase transcript half-life (Banerjee et al, 2009). Although we have predominantly used tissue-level expression data, mobile transcripts are also highly abundant in companion cells relative to nonmobile (Supplemental Figure 4).…”

Signaling pathway in development of Camellia oleifera nurse seedling grafting union

“…It is also employed in plant propagation, including trees (Sanou et al 2004;Mencuccini et al 2007), vegetables (Kubota et al 2008), and flowers (Ginova et al 2012). Moreover, it is an important method applied in studies addressing shoot-root physiological relationships (Sakamoto and Nohara 2009;Han et al 2013), resistance mechanisms (Sugawara et al 2013), material transport (Lin et al 2007;Flaishman et al 2008;Zhang et al 2012), flowering regulation (Yoo et al 2013), and long-distance signal transmission mechanisms (Chen et al 2006;Banerjee et al 2009). …”