Leaf Plasmodesmata Respond Differently to TMV, ToBRFV and TYLCV Infection

Tomato Brown Rugose Fruit Virus Pandemic

Tomato brown rugose fruit virus (ToBRFV) is an emerging tobamovirus. It was first reported in 2015 in Jordan in greenhouse tomatoes and now threatens tomato and pepper crops around the world. ToBRFV is a stable and highly infectious virus that is easily transmitted by mechanical means and via seeds, which enables it to spread locally and over long distances. The ability of ToBRFV to infect tomato plants harboring the commonly deployed Tm resistance genes, as well as pepper plants harboring the L resistance alleles under certain conditions, limits the ability to prevent damage from the virus. The fruit production and quality of ToBRFV-infected tomato and pepper plants can be drastically affected, thus significantly impacting their market value. Herein, we review the current information and discuss the latest areas of research on this virus, which include its discovery and distribution, epidemiology, detection, and prevention and control measures, that could help mitigate the ToBRFV disease pandemic.

Meristematic Connectome: A Cellular Coordinator of Plant Responses to Environmental Signals?

Mechanical stress in tree roots induces the production of reaction wood (RW) and the formation of new branch roots, both functioning to avoid anchorage failure and limb damage. The vascular cambium (VC) is the factor responsible for the onset of these responses as shown by their occurrence when all primary tissues and the root tips are removed. The data presented confirm that the VC is able to evaluate both the direction and magnitude of the mechanical forces experienced before coordinating the most fitting responses along the root axis whenever and wherever these are necessary. The coordination of these responses requires intense crosstalk between meristematic cells of the VC which may be very distant from the place where the mechanical stress is first detected. Signaling could be facilitated through plasmodesmata between meristematic cells. The mechanism of RW production also seems to be well conserved in the stem and this fact suggests that the VC could behave as a single structure spread along the plant body axis as a means to control the relationship between the plant and its environment. The observation that there are numerous morphological and functional similarities between different meristems and that some important regulatory mechanisms of meristem activity, such as homeostasis, are common to several meristems, supports the hypothesis that not only the VC but all apical, primary and secondary meristems present in the plant body behave as a single interconnected structure. We propose to name this structure “meristematic connectome” given the possibility that the sequence of meristems from root apex to shoot apex could represent a pluricellular network that facilitates long-distance signaling in the plant body. The possibility that the “meristematic connectome” could act as a single structure active in adjusting the plant body to its surrounding environment throughout the life of a plant is now proposed.