Ethylene Response Factors Are Controlled by Multiple Harvesting Stresses in Hevea brasiliensis

Abstract

Tolerance of recurrent mechanical wounding and exogenous ethylene is a feature of the rubber tree. Latex harvesting involves tapping of the tree bark and ethephon is applied to increase latex flow. Ethylene is an essential element in controlling latex production. The ethylene signalling pathway leads to the activation of Ethylene Response Factor (ERF) transcription factors. This family has been identified in Hevea brasiliensis. This study set out to understand the regulation of ERF genes during latex harvesting in relation to abiotic stress and hormonal treatments. Analyses of the relative transcript abundance were carried out for 35 HbERF genes in latex, in bark from mature trees and in leaves from juvenile plants under multiple abiotic stresses. Twenty-one HbERF genes were regulated by harvesting stress in laticifers, revealing an overrepresentation of genes in group IX. Transcripts of three HbERF-IX genes from HbERF-IXc4, HbERF-IXc5 and HbERF-IXc6 were dramatically accumulated by combining wounding, methyl jasmonate and ethylene treatments. When an ethylene inhibitor was used, the transcript accumulation for these three genes was halted, showing ethylene-dependent induction. Subcellular localization and transactivation experiments confirmed that several members of HbERF-IX are activator-type transcription factors. This study suggested that latex harvesting induces mechanisms developed for the response to abiotic stress. These mechanisms probably depend on various hormonal signalling pathways. Several members of HbERF-IX could be essential integrators of complex hormonal signalling pathways in Hevea.

The rubber tree genome reveals new insights into rubber production and species adaptation

“…Ethylene treatment triggers a number of stimulated downstream biochemical cascades in relation to latex production: sugar loading and its catabolism 9,36,39,40 , water uptake 41 , energy availability 42 , cytosolic alkalinization 42 , nitrogen assimilation 43 and defence responses 44 . Many genes implicated in these events were among the DEGs identified in this study (Supplementary Tables 22 and 23), but not the rubber biosynthesis genes, which is consistent with the previous proposition that ethylene has little direct effect on genes in rubber biosynthesis 45 .…”

The Hevea brasiliensis AP2/ERF superfamily: from ethylene signalling to latex harvesting and physiological disease response

“…However, these GEMs may or may not have all important function in rubber tree. Putranto et al (2015b) and Putranto et al (2015a) In general results, high relative abundance of transcripts were detected in several groups of HbAP2/ERFs 2015a;2015b). Although some members of these groups have not proven to be GEMs, high level of expression leads us to suggest their involvement in some regulation at the molecular level.…”

“…In parallel with the work of Piyatrakul, the characterization of Hevea AP2/ERF superfamily was similarly addressed by studying their stress response as well as during the occurrence of tapping panel dryness (Table 1) (Putranto et al, 2015b, Putranto et al, 2015a was identified using high-debit qPCR analysis from the juvenile plant samples which were generated from the somatic embryogenesis prepared in CIRAD (Putranto et al, 2015a).…”

“…Duan et al (2013) was also used this database to construct the classification of Hevea AP2/ERF transcription factors. The bibliographic and phylogenetic analyses were able to reveal the potential functions of these GEMs (Putranto et al, 2015a. However, these GEMs may or may not have all important function in rubber tree.…”

“…Marka-marka tersebut disarikan dari Putranto et al (2015aPutranto et al ( , 2015b. shown in red meanwhile the downregulated GEMs were in blue colour.…”