Functional Analysis of Two Orthologous NAC Genes, CarNAC3, and CarNAC6 from Cicer arietinum, Involved in Abiotic Stresses in Poplar

Abstract

Abiotic stresses such as drought and high salinity inhibit plant growth and productivity. NAC transcription factors play a variety of important roles in plant development and abiotic stress responses. To date, the transformation of NAC genes into poplar plants has not been reported. In this study, we introduced the CarNAC3 and CarNAC6 salinity and drought tolerant genes from Cicer arietinum (chickpea) into Populus deltoides × Populus euramericana ‘Nanlin895’ (poplar) plants using Agrobacterium tumefaciens-mediated transformation. We verified the integration of the two genes into the poplar genome using polymerase chain reaction (PCR) and their stable expression was confirmed at the transcript level using real-time (RT)-PCR. The growth rates of roots and shoots and the clawed root rate increased in transformed plants grown in agar medium or in soil and increased in response to drought and salt stress conditions. Proline and photoprotectant pigment accumulation and antioxidant enzyme activities increased in response to abiotic stress, but the accumulation of photosynthetic pigments and malondialdehyde (MDA) decreased in transgenic lines relative to wild-type control plants. The CarNAC3 transgene was expressed at higher levels than the CarNAC6 transgene. Our results showed that the CarNAC3 and CarNAC6 genes enhanced the capacity for osmotic adjustment and increased antioxidant enzyme activity and suggest that these genes could play a significant role in improving drought and salt tolerance when expressed in poplar plants.