Transcriptome analysis in Hevea brasiliensis latex revealed changes in hormone signalling pathways during ethephon stimulation and consequent Tapping Panel Dryness

Pascal Montoro,Maryannick Rio,Marie-Laure Martin-Magniette,Sigit Ismawanto,Shuangyang Wu,Cécile Labrune,Stéphanie Pointet,Bénédicte Favreau,Julie Leclercq,Kuswanhadi Kuswanhadi,Eva Herlinawati

doi:10.1038/s41598-018-26854-y

Abstract

Tapping Panel Dryness (TPD) affects latex production in Hevea brasiliensis. This physiological syndrome involves the agglutination of rubber particles, which leads to partial or complete cessation of latex flow. Latex harvesting consists in tapping soft bark. Ethephon can be applied to stimulate latex flow and its regeneration in laticifers. Several studies have reported transcriptome changes in bark tissues. This study is the first report on deep RNA sequencing of latex to compare the effect of ethephon stimulation and TPD severity. Trees were carefully selected for paired-end sequencing using an Illumina HiSeq 2000. In all, 43 to 60 million reads were sequenced for each treatment in three biological replicates (slight TPD trees without ethephon stimulation, and slight and severe TPD trees with ethephon treatment). Differentially expressed genes were identified and annotated, giving 8,111 and 728 in response to ethephon in slight TPD trees and in ethephon-induced severe TPD trees, respectively. A biological network of responses to ethephon and TPD highlighted the major influence of metabolic processes and the response to stimulus, especially wounding and jasmonate depression in TPD-affected trees induced by ethephon stimulation.

Highlights

Natural rubber produced by Hevea brasiliensis accounts for more than 40% of rubber consumption worldwide
Trees were classified as slight or severe Tapping Panel Dryness (TPD) depending on the mean dry cut length (DCL) over the last 12 months of tapping before sampling (Table 1)
This study reports on the first deep RNA sequencing in the latex of ethephon-induced TPD-affected trees

Summary

Introduction

Natural rubber produced by Hevea brasiliensis accounts for more than 40% of rubber consumption worldwide. An irreversible type of TPD, called brown bast (BB), occurs This form is related to deformation of the bark due to thylosoid formation, lignified gum, and abnormal division of parenchyma cells, and may be related to a cyanogenesis process[4,5]. Given the stoppage in latex flow, deep sequencing of RNA has focused solely on bark tissues of severe TPD-affected trees. These analyses notably revealed a down-regulation of genes related to rubber biosynthesis[17] as well as jasmonate production[18]. This study identified 728 differentially expressed genes associated with ethephon-induced TPD, 272 of which were regulated by TPD and not by ethephon treatment. When ethephon-induced TPD became established, an overall decrease in gene expression was observed, except for genes related to the GO “stimulus response” term, those related to the wounding and jasmonic acid pathways

Methods

Results

Conclusion