Function and regulation of plant major intrinsic proteins: the role in arsenic accumulation

Research output: Book/ReportPh.D. thesisResearch

  • Milan Popovic
Arsenic is a metalloid that is toxic to living organisms. The use of arsenic-contaminated ground water for drinking and for irrigation in agriculture presents serious health problems for millions of people in many parts of the world. Arsenate (As(V)) and arsenite (As(III)), the two most widespread inorganic forms of arsenic in the environment, can be taken up by plants and thus enter the food chain. Once inside the root cells, As(V) is reduced to As(III) which is then extruded to the soil solution or bound to phytochelatins (PCs) and transported to the vacuole in an effort to accomplish detoxification.
Plant Noduline 26-like Intrinsic Proteins (NIPs) can channel As(III) and consequently influence the detoxification process. The role of the Tonoplast Intrinsic Proteins (TIPs) in As(III) detoxification remains to be clarified, yet TIPs could have an impact on As(III) accumulation in plant cell vacuoles. In this study using Arabidopsis, the role of TIP subfamily in arsenic transport was examined together with the role of N-terminus in regulation of AtNIP5;1, which has previously been shown to transport As(III) in a yeast expression system. The results showed that AtTIP4;1 functions as a bidirectional channel for As(III) and to some extent to antimonite (Sb(III)), when expressed in yeast. Moreover, a direct transport assays confirmed the ability of AtTIP4;1 to mediate As(III) transport across the yeast cell membrane. A reverse genetic approach was used to characterize the role of AtTIP4;1 in Arabidopsis. That led to the discovery that tip4;1 is gametophytic lethal- gene essential for normal seed set. ICP-MS analyses of the elemental composition of tip4;1 heterozygous T-DNA insert mutant plants and 35S::TIP4;1 over-expression plants indicate that AtTIP4;1 has a role in arsenic distribution in Arabidopsis. The function of N-terminus in regulation of AtNIP5;1 in planta remains elusive. ICPMS analysis of the elemental composition and expression analysis did not clarify the role of Nterminus of AtNIP5;1 in arsenic accumulation in Arabidopsis. Further research is needed to elucidate the role of N-terminus in regulation of arsenic accumulation in plants.
In this work the first plant TIP that channels As(III) was reported. It is suggested that AtTIP4;1 may have a role in the early stages of As(III) detoxification by mediating As(III) entry to the vacuole. This mechanism would work in concert with binding of As(III) by PCs. There is thus great interest in perceiving mechanisms of transport and detoxification of arsenic in order to improve soil management and crops through breeding and iotechnology. This result is important for the further understanding of arsenic etoxification mechanisms which could eventually lead to development of plants with levated arsenic tolerance. Plants with the ability to hyperaccumulate arsenic could find its use in soil remediation while crop plants with efficient arsenic detoxification mechanisms could be used for food production in areas polluted with arsenic.
Original languageEnglish
PublisherDepartment of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen
Number of pages108
Publication statusPublished - 2013

ID: 46405839