Vertical and Horizontal Transmission of Pospiviroids.

Teruo Sano,Hironobu Yanagisawa,Yosuke Matsushita

doi:10.3390/v10120706

Abstract

Viroids are highly structured, single-stranded, non-protein-coding circular RNA pathogens. Some viroids are vertically transmitted through both viroid-infected ovule and pollen. For example, potato spindle tuber viroid, a species that belongs to Pospiviroidae family, is delivered to the embryo through the ovule or pollen during the development of reproductive tissues before embryogenesis. In addition, some of Pospiviroidae are also horizontally transmitted by pollen. Tomato planta macho viroid in pollen infects to the ovary from pollen tube during pollen tube elongation and eventually causes systemic infection, resulting in the establishment of horizontal transmission. Furthermore, fertilization is not required to accomplish the horizontal transmission. In this review, we will overview the recent research progress in vertical and horizontal transmission of viroids, mainly by focusing on histopathological studies, and also discuss the impact of seed transmission on viroid dissemination and seed health.

Highlights

Viroids are the smallest, self-replicating, non-coding RNAs capable of inducing multiple disease symptoms in susceptible host plants, including potato, tomato, cucumber, hop, coconut, grapevine, fruit trees, and some ornamental plants [1,2]
These findings indicate that tissues the success embryo invasion by the and virus depends on the developmental findings indicate that the success stage of the reproductive organs. of embryo invasion by the virus depends on the developmental stage of the reproductive organs
The rate of horizontal transmission was very high in petunia plants when they were pollinated with tomato planta macho viroid (TPMVd)-infected petunia pollen grains, horizontal transmission was when they were pollinated with TPMVd-infected petunia pollen grains, horizontal transmission was not observed at all in petunia pollinated with potato spindle tuber viroid (PSTVd)-infected pollen [32]

Summary

Introduction

Self-replicating, non-coding RNAs capable of inducing multiple disease symptoms in susceptible host plants, including potato, tomato, cucumber, hop, coconut, grapevine, fruit trees (apple, avocado, citrus, peach, pear and plum), and some ornamental plants (chrysanthemum and coleus) [1,2]. It is known as vertical transmission (Figure 1) [6,7,8,9]. Even vertically plant viruses and viroids are known to spread horizontally or even vertically through pollen through pollen in experimental conditions, but for the viroids at least, the effects of these types in of experimental but for the viroids at least, the been effectsclearly of these types of transmission on actual transmissionconditions, on actual plant cultivation have not yet understood. Recent experimental results suggested thatnot horizontal transmission causes spreadingresults of thesuggested viroid tothat the horizontal transmission causes spreading of the viroid to the surrounding host of the same surrounding host of the same species, and provides a chance to propagate in other host species.

Factors

Mechanism of Seed Transmission

Mechanism of Horizontal Transmission

Findings

Further Prospects