Abstract
Molybdenum (Mo) is an essential micronutrient in many plants. In the rubber tree Hevea brasiliensis, Mo application can reduce the shrinkage of the tapping line, decrease tapping panel dryness, and finally increase rubber latex yield. After combined Mo with ethylene (Eth), these effects become more obvious. However, the molecular mechanism remains unclear. Here, we compared the changed patterns of physiological parameters and protein accumulation in rubber latex after treated with Mo and/or Eth. Our results demonstrated that both Eth and Mo can improve the contents of thiol, sucrose, and dry yield in rubber latex. However, lutoid bursting is significantly inhibited by Mo. Comparative proteomics identified 169 differentially expressed proteins, including 114 unique proteins, which are mainly involved in posttranslational modification, carbohydrate metabolism, and energy production. The abundances of several proteins involved in rubber particle aggregation are decreased upon Mo stimulation, while many enzymes related to natural rubber biosynthesis are increased. Comparison of the accumulation patterns of 25 proteins revealed that a large portion of proteins have different changed patterns with their gene expression levels. Activity assays of six enzymes revealed that Mo stimulation can increase latex yield by improving the activity of some Mo-responsive enzymes. These results not only deepen our understanding of the rubber latex proteome but also provide new insights into the molecular mechanism of Mo-stimulated rubber latex yield.
Highlights
Natural rubber, a very long chain of cis-1,4-polyisoprene polymer, is generated from over 2,500 plant species, but the rubber tree Hevea brasiliensis is the only commercially cultivated one (van Beilen and Poirier, 2007)
Our results showed that Eth and ammonium molybdate can improve rubber latex yield by regulating the accumulation of proteins involved in rubber particle aggregation (RPA), latex coagulation, rubber biosynthesis, and antioxidant response
Proteins involved in mevalonate (MVA) pathway are crucial for natural rubber biosynthesis (NRB) (Wang et al, 2015)
Summary
A very long chain of cis-1,4-polyisoprene polymer, is generated from over 2,500 plant species, but the rubber tree Hevea brasiliensis is the only commercially cultivated one (van Beilen and Poirier, 2007). Strong tapping can promote the accumulation of active oxygen, disturb the imbalance between peroxidation activity and scavenging activity, increase the lutoid rupture and release of coagulation factors, cause the in situ coagulation of latex, and result in the occurrence of tapping panel dryness (Putranto et al, 2015) This stimulation effect is associated with marked changes in both physiology and metabolism of laticifer, including the contents of dry rubber, total thiol, sucrose, Mg2+, and inorganic phosphorus; turgor pressure and lutoid stability; latex regeneration; sucrose transport, nucleotide acid, and protein synthesis; adenine nucleotide pools; and compartmental ion balance (Coupé and Chrestin, 1989; Lestari et al, 2017)
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