Contrasting tolerance and gene expression between white pine (Pinus strobus) and jack pine (P. banksiana) exposed to an increasing nickel concentration

Abstract

Studies on copying mechanisms of Pinus strobus and P. banksiana to soil metal contamination are limited. The objectives of this study were to 1) determine if P. strobus or P. banksiana are Ni resistant 2) If Ni associated genes will show differential expression under increasing concentration of Ni; and 3) if Ni mobility and accumulation in these two species show different patterns. We determined how these two species respond to soil nickel contamination. Damage ratings revealed that P. banksiana is susceptible to high concentration of Ni(NO 3 ) 2 (1600 and 3200 mg/kg) while P. strobus was tolerant. Soil nickel treatments induced a downregulation of high affinity- Ni transporter family AT2G16800 and Natural resistance-associated macrophage proteins ( NRAMP3 ) in both species with the severity increasing at high levels of Ni. A concentration-dependent response of 1-aminocyclopropane-1-carboxylic acid deaminase ( ACC deaminase ) in both species consistent with the hormetic effects was observed. Nickel triggered also a concentration-dependent downregulation of serine acetyltransferase ( SAT ) in P. strobus with the lowest concentration showing the highest repression. An opposite trend was observed in P. banksiana where Ni induced an upregulation of SAT . Interestingly, the mobility of Ni in the two pine tissues showed a similar pattern. Analysis of response of P. strobus and P. banksiana to nickel in metal contaminated lands showed an uptake of Ni from the rhizospheres and its bioaccumulation in roots. The Ni translocation from roots to branches or needles showed limited to moderate mobility of Ni ions to aerial parts with no significant accumulation in those tissues.