Functional Characterization Of Aquaporins(HbPIP1and HbPIP2) In Hevea Brasiliensis And The Relationship Between Their Expression And Latex Physiological Parameters

Function and expression profiles of Aquaporins (HbPIP1and HbPIP2) in PR107Hevea brasiliensis that is sensitive to ethrel stimulation were examined in this study. We applied2.5%ethrel at different time before tapping, the barks latic, and latex in different periods of the flow course were collected. Meanwhile, the influences of ethrel stimulation on the expression of HbPIP1in the transcription level and translation level by RT-PCR and western blot were examined toinvestigate its impact on the latex physiological. The results show:(1)HbPIPl has the function of the water transportation, whilst HbPIP2has not.(2)The expression of HbPIP1in latex, bark and xylem is higher than that in various periods of petioles and blades, and expression of HbP IP2in bark is higher than other organs.(3)After brushing ethrel, the expression of HbPIP1in latex of PR107presents a clear rising trend no matter in the transcription level or translation level; expression of HbPIP1in bark of PR107rubber tree tends to reduce, before24h, expression of HbPIP1in bark is lower than CK all the time; thiol content, inorganic phosphor content, sugor content, lutoid bursting index of latex all have obvious change; latex flow duration and latex volume are markedly increased, DRC and TSC of latex are decreased.(4)In the latex flow course, expression of HbPIP1in the different latex fractions presents a clear rising trend no matter in the transcription level or translation level; however, the time when HbPIP1expression increases in the ethrel stimulated tree is later and last longer acompared to those untreated trees.(5) Expression of HbPIP1and HbPIP2substantially increases at3h after ethrel stimulation, then the expression level decreases but is still significantly higher than control in40h which proves that ethrel stimulation could make aquaporins consistently express, so DRC of latex decreases and latex flow duration increases. However, latex production of Hevea brasiliensis is a dynamic equilibrium system, ethrel stimulation promotes latex regeneration which enhances the metabolism of latex vessels, consumes more sucrose, produces more by-products like toxic oxygen for which Hevea brasiliensis needs more thoil to clear metabolic by-products, and more inorganic phosphorus involves in energy metabolism…… There is a dynamic relationship between those changes of latex physiological parameters and upregulation of aquaporins of Hevea brasiliensis.All in all, these results proved that ethrel stimulation promotes latex yield by regulating the expression of aquaporins. After ethrel stimulation, expression of HbPIP1in latex increased, this facilitated the water movement to laiticifer vessels and thendiluted the latex, so latex flow will be prlonged; in the flow course, HbPIP1expression increases in the ethrel stimulated tree is later and last longer acompared to those untreated trees, so ethrel stimulation extends latex flow duration and increase latex volume.