Involvement of Ethylene in the Latex Metabolism and Tapping Panel Dryness of Hevea brasiliensis

Abstract

Ethephon, an ethylene releaser, is used to stimulate latex production in Hevea brasiliensis. Ethylene induces many functions in latex cells including the production of reactive oxygen species (ROS). The accumulation of ROS is responsible for the coagulation of rubber particles in latex cells, resulting in the partial or complete stoppage of latex flow. This study set out to assess biochemical and histological changes as well as changes in gene expression in latex and phloem tissues from trees grown under various harvesting systems. The Tapping Panel Dryness (TPD) susceptibility of Hevea clones was found to be related to some biochemical parameters, such as low sucrose and high inorganic phosphorus contents. A high tapping frequency and ethephon stimulation induced early TPD occurrence in a high latex metabolism clone and late occurrence in a low latex metabolism clone. TPD-affected trees had smaller number of laticifer vessels compared to healthy trees, suggesting a modification of cambial activity. The differential transcript abundance was observed for twenty-seven candidate genes related to TPD occurrence in latex and phloem tissues for ROS-scavenging, ethylene biosynthesis and signalling genes. The predicted function for some Ethylene Response Factor genes suggested that these candidate genes should play an important role in regulating susceptibility to TPD.

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

“…Marka-marka tersebut disarikan dari Putranto et al (2015aPutranto et al ( , 2015b (Khandelwal et al, 2008) Taken together, the result of differential gene expression analysis by Duan et al (2013) and Putranto et al (2015a) has brought into conclusion that HbERF-IXc4 and HbERF-IXc5 could have a major role in the regulation of latex production as they were highly expressed in bark during latex harvesting. The ERF group VIII contains an ERF-associated amphiphilic repression (EAR)-motif known as the transcriptional repressors (Ohta et al, 2001).…”

“…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.…”

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

“…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).…”

“…LH = latex harvesting; T = tapping; Et-= no ethephon treatment; Et+ = ethephon treatment. The GEMs were extracted from Putranto et al (2015aPutranto et al ( , 2015b) (cont. ).…”