The mRNA mobileome: challenges and opportunities for deciphering signals from the noise

Abstract

Organismal communication entails encoding a message that is sent over space or time to a recipient cell, where that message is decoded to activate a downstream response. Defining what qualifies as a functional signal is essential for understanding intercellular communication. In this review, we delve into what is known and unknown in the field of long-distance messenger RNA (mRNA) movement and draw inspiration from the field of information theory to provide a perspective on what defines a functional signaling molecule. Although numerous studies support the long-distance movement of hundreds to thousands of mRNAs through the plant vascular system, only a small handful of these transcripts have been associated with signaling functions. Deciphering whether mobile mRNAs generally serve a role in plant communication has been challenging, due to our current lack of understanding regarding the factors that influence mRNA mobility. Further insight into unsolved questions regarding the nature of mobile mRNAs could provide an understanding of the signaling potential of these macromolecules.

Traveling with purpose: cell-to-cell transport of plant mRNAs

“…For mRNAs to be transported over long distances, they need to be imported into the phloem at their source, and exported from the phloem at their destination. The companion cells serve as stations for this purpose [5]; they are connected by PDs and transport signals to the phloem sieve elements. PDs are highly regulated channels [2,6,7], and may confer selectivity between companion cells and sieve elements for long-distance mRNA transport [4,8].…”

“…Long-distance mRNA transport via the phloem has been widely studied [4,5,17]. Grafting experiments combined with transcriptome analysis identified hundreds to thousands of mobile mRNAs Highlights mRNAs traffic between plant cells/ tissues/organs via plasmodesmata (PDs) and the phloem to act as noncell-autonomous signals controlling diverse biological processes.…”

Citrus threat huanglongbing (HLB) - Could the rootstock provide the cure?

“…5 Root-to-shoot transport of RNAs from transgenic donor rootstocks can fight HLB in non-transgenic scions Plants use long-distance signaling to coordinate responses to external biotic and abiotic stress (Takahashi and Shinozaki, 2019). This long-distance communication may include metabolites, hormones, proteins, peptides, electrical signals, and small RNAs, while messenger RNAs (mRNAs) might be the most common signal vehicle (Heeney and Frank, 2023). tRNA-like structures (TLSs) are sufficient to mediate mRNA transport and are essential for the mobility of a large number of transcripts that can move through the graft junction between rootstock and scion.…”

Large-scale interplant exchange of macromolecules between soybean and dodder under nutrient stresses

“…The growth and development of dodder rely entirely on the host plants, and it is very likely that these two interacting organisms constantly communicate using systemic signals, which could be the mobile mRNAs and proteins. Recently, the term mobileome/mobilome has been used to describe the collective contents of mobile macromolecules ( Heeney and Frank, 2023 ). Here, in addition to studying the transcriptomic and proteomic responses of soybean and the parasitizing dodder to N and P starvation, we specifically focused on the mRNA and protein mobileomes between dodder and soybean hosts under normal and nutrient deficiency conditions.…”