Physical Characteristics of the Leaves and Latex of Papaya Plants Infected with the Papaya meleira Virus.

Jean Carlos Vencioneck Dutra,Antonio Alberto Ribeiro Fernandes,Raúl Tapia-Tussell,Anuar Magaña-Álvarez,Inocencio Higuera-Ciapara,Patricia Machado Bueno Fernandes,Jose Aires Ventura,Daisy Pérez-Brito,Tarcio Carneiro

doi:10.3390/ijms17040574

Abstract

Sticky disease, which is caused by Papaya meleira virus (PMeV), is a significant papaya disease in Brazil and Mexico, where it has caused severe economic losses, and it seems to have spread to Central and South America. Studies assessing the pathogen-host interaction at the nano-histological level are needed to better understand the mechanisms that underlie natural resistance. In this study, the topography and mechanical properties of the leaf midribs and latex of healthy and PMeV-infected papaya plants were observed by atomic force microscopy and scanning electron microscopy. Healthy plants displayed a smooth surface with practically no roughness of the leaf midribs and the latex and a higher adhesion force than infected plants. PMeV promotes changes in the leaf midribs and latex, making them more fragile and susceptible to breakage. These changes, which are associated with increased water uptake and internal pressure in laticifers, causes cell disruption that leads to spontaneous exudation of the latex and facilitates the spread of PMeV to other laticifers. These results provide new insights into the papaya-PMeV interaction that could be helpful for controlling papaya sticky disease.

Highlights

Papaya (Carica papaya L.) production currently amounts to approximately 12 million tons per year worldwide, and Brazil and Mexico are the main exporting countries [1]
Meleira, which is caused by the Papaya meleira virus (PMeV), is responsible for severe economic losses that can affect between 50% and 80% of the total production [2]
When infected by PMeV, papaya plants spontaneously exudate the latex from leaves and fruits

Summary

Introduction

Papaya (Carica papaya L.) production currently amounts to approximately 12 million tons per year worldwide, and Brazil and Mexico are the main exporting countries [1]. We observed that virus activity leads to changes in the microstructures of the leaf midribs and latex of the infected plants, promoting increased surface roughness This result corroborates the suggestion of Rodrigues et al 2009 [7] that some classes of papaya cells, such as laticifers, behave differently when infected by the sticky disease virus. Plants reduce the pore diameter of their plasmodesmata to limit the mobility of viruses [20], but PMeV counteracts this strategy by interfering with the physiology of the laticifers to compromise the assembly of the latex particles (Figure 6), increasing the water uptake [7] and making the latex from the sticky diseased papaya more fluid and translucent than its healthy counterpart [6]. The results of this work provide new insights into the interaction between papaya and PMeV, which could contribute to the control of papaya sticky disease and the development of a genetically modified papaya

Leaf Midrib and Latex Collection

Findings

Image Acquisition