Abstract
Included among the many signals that traffic through the sieve element system are full-length mRNAs that function to respond to the environment and to regulate development. In potato, several mRNAs that encode transcription factors from the three-amino-loop-extension (TALE) superfamily move from leaves to roots and stolons via the phloem to control growth and signal the onset of tuber formation. This RNA transport is enhanced by short-day conditions and is facilitated by RNA-binding proteins from the polypyrimidine tract-binding family of proteins. Regulation of growth is mediated by three mobile mRNAs that arise from vasculature in the leaf. One mRNA, StBEL5, functions to activate growth, whereas two other, sequence-related StBEL’s, StBEL11 and StBEL29, function antagonistically to repress StBEL5 target genes involved in promoting tuber development. This dynamic system utilizes closely-linked phloem-mobile mRNAs to control growth in developing potato tubers. In creating a complex signaling pathway, potato has evolved a long-distance transport system that regulates underground organ development through closely-associated, full-length mRNAs that function as either activators or repressors.
Highlights
StSP6A, an and are both previous work, the three important signals that regulate the onset of tuber formation in potato previous most important signals that regulate the onset of tuber formation in potato seven RNAs indicate the prominent the mobile transcript through a graft union
Developmental studies with StBEL5 overexpression and suppression lines demonstrated a very strong positive correlation between StBEL5 and StSP6A gene activity [29]. It is through this overall pattern of transcriptional control and its targeted RNA mobility that StBEL5 affects its impact on tuber formation [9,29]
Mobility and Function of StBEL11 and StBEL29. Because of their close sequence matches, including highly conserved functional domains and accumulation in stolons during the onset of tuber formation, we considered the possibility that members of the StBEL5/StBEL11/StBEL29 clade of StBEL-like transcription factors (TFs) share both the mode of action and function in relation to tuber development
Summary
Plants have evolved a unique long-distance signaling system that utilizes cell-to-cell plasmodesmatal connections and a specialized phloem cell network. PFP-LeT6 from phloem-dependent allocation pathway from leaves to roots, a mobile high number of transcripts established function or phenotype are still rare. PFP-LeT6 from phloem-dependent sugar allocation pathway from leaves to roots, but a high number of transcripts phloem system and play important roles in both defense and development miRNAs established function or important phenotype are in still rare. PFP-LeT6 from phloem-dependent sugar allocation pathway from leaves roots, but a high number of transcripts have identified in potato [19,20], and two ofof these, miR172 andalso miR156, have been implicated in Inbeen addition to full-length. Some ofsignals the examples of these latter types role in regulating the of full-length, mobile have been identified inactivity potato [19,20], and of these, miR172 andbest phloem system and-11, play important roles insmall both defense andTdevelopment mRNAs, RNAs/miRNAs are mobile through the[23]. RNAs indicate the prominent of the mobile transcript through graft union
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