Characterization of Polypeptides Accumulated in the Latex Cytosol of Rubber Trees Affected by the Tapping Panel Dryness Syndrome

Abstract

The tapping panel dryness (TPD) syndrome of rubber is characterized by the reduction or ultimately total cessation of latex flow upon tapping, due to physiological disorders in the bark tissue. The protein pattern in the cytoplasm from healthy and TPD tree latex cells was compared by electrophoresis. Two polypeptides (P15 and P22) of 15 and 22 kDa, respectively, were found to accumulate in the cytosol of the TPD-affected trees, whereas a 29 kDa polypeptide (P29) appeared de novo. P15 and P22 were identified as REF (Hev b1) and SRPP (Hev b3), respectively, two proteins proposed to be involved in rubber biosynthesis. P29 appeared to be a new member of the patatinlike protein family. Specific molecular probes were designed for a detailed characterization of REF and SRPP gene expression and RFLP mapping. This allowed the demonstration that REF and SRPP display very similar expression profiles. They are highly over-expressed by the tappinginduced metabolic activation, although not by wounding per se, or ethylene or ABA. In addition to this similarity in gene expression, they were found to share one common locus in the genome. No significant difference in REF and SRPP gene expression was observed between healthy and TPD trees, indicating that their TPD-related accumulation in the cytosol was not transcriptionally regulated. Western blot analysis demonstrated that osmotic lysis of the sedimentable organelles (lutoids) in vitro caused the release of REF and SRPP from the rubber particle membrane into the cytosol. A mechanism of cellular delocalization as a consequence of the lutoids instability is proposed to explain REF and SRPP accumulation in the cytosol of TPD trees.

Lipid Droplet-Associated Proteins (LDAPs) Are Required for the Dynamic Regulation of Neutral Lipid Compartmentation in Plant Cells

“…For instance, the LDAP genes and their SRPP counterparts are strongly induced in some plants in response to abiotic stress (Sookmark et al, 2002;Priya et al, 2007;Kim et al, 2010;Seo et al, 2010;Fricke et al, 2013) as well as ectopic application of abscisic acid, as indicated by the Arabidopsis eFP Browser microarray database (Winter et al, 2007). LDs are also known to be involved in lipid metabolism associated with pathogen infection (Herker and Ott, 2012;Murphy, 2012), and biochemical studies have shown a significant increase in TAG and neutral lipids in plants subjected to heat, cold, drought, and salt stress (Mueller et al, 2015;Tarazona et al, 2015).…”

“…In LDAP-disrupted plant lines, however, there were no significant decreases in neutral lipid content, although ldap3-1 and ldap3-2 mutant lines did show modest increases in neutral lipid abundance ( Fig. 3C Prior studies revealed that LDAP genes are strongly induced during abiotic stress responses in a variety of plant species (Sookmark et al, 2002;Priya et al, 2007;Kim et al, 2010;Seo et al, 2010;Fricke et al, 2013), and more recent studies have shown that neutral lipid content, particularly TAG, is increased in response to cold or heat (Mueller et al, 2015;Tarazona et al, 2015). Given that LDAPs target to LDs (Figs.…”

Involvement of HbPIP2;1 and HbTIP1;1 Aquaporins in Ethylene Stimulation of Latex Yield through Regulation of Water Exchanges between Inner Liber and Latex Cells in Hevea brasiliensis

“…The proteins were either stained with Coomassie Brilliant Blue (Sambrook et al, 1989) or electroblotted onto a polyvinylidene difluoride membrane according to Towbin et al (1979). Immunostaining was performed as described by Sookmark et al (2002), except that the HbPIP2;1 antibody (1:500), the alkaline phosphatase-conjugated goat anti-rabbit antibody (1:5,000), and the 5-bromo-4-chloro-3-indolyl phosphate/nitroblue tetrazolium substrate (Roche) were used. The intensity of the protein bands was scanned using the Quantify One program version 4.2.3 (Bio-Rad).…”

Genomics of Hevea Rubber

“…9.10 ). In later stage, the tapping panel becomes completely dry, and other symptoms such as browning, thickening, and fl aking of bark can occur (Sookmark et al 2002 ) . A great deal of work was performed to reveal the nature and molecular mechanisms leading to TPD.…”

“…Increased bark respiration due to TPD was demonstrated by Krishnakumar et al ( 2001 ) . Proteins related to TPD were identi fi ed by comparing the expression patterns between healthy and TPD-affected trees (Dian et al 1995 ;Lacrotte et al 1995 ;Sookmark et al 2002 ) , but their functional relations with TPD still remain unknown. Therefore, it is necessary to identify the genes associated with TPD to unravel the molecular mechanisms involved.…”