Overexpression of NAC gene from Lepidium latifolium L. enhances biomass, shortens life cycle and induces cold stress tolerance in tobacco: potential for engineering fourth generation biofuel crops

Abstract

We report elevated biomass and altered growth characteristics of tobacco plants up on transformation with a NAC (NAM, ATAF1/2,CUC2) gene (GenBank Accession FJ754254) isolated from Lepidium latifolium L. (LlaNAC). Transgenic plants showed significant differences in fresh weight, midrib length of longest leaf, leaf area, height of the plant, root and shoot weights, etc. during vegetative phase. On 100th day after sowing (DAS), plants of transgenic lines were 2-3 times taller than the wild type plants, though no significant difference was recorded in moisture contents of any of the plant tissues. Over-expression of NAC gene up to 2,000 fold was recorded in leaves of transgenic plants on 100th DAS. Interestingly, transgenic plants showed significantly shortened (P(t) = 0.02-0.04) life cycle, as they showed a completely altered growth behaviour. Transgenic plants entered reproductive phase earlier by 60 days, with lines NC2 and NC7b entering first, followed by line NC10. However, the time period spent in the reproductive phase by the plant was nearly twice in case of transgenic lines NC2, NC7b and NC10, as compared to the wild type plants. Despite that, these lines completed their life cycle in 45-60 days lesser than the time taken by wild-type tobacco plants. No difference was recorded in fruit and seed yield of transgenic or wild type plants. To the best of our knowledge, this is the first report on over-expression of NAC gene causing altered growth and biomass patterns. We expect this study to become an important reference towards future engineering of plants for fuel and fodder purposes.

Activation of miR165b represses AtHB15 expression and induces pith secondary wall development in Arabidopsis

“…Several closely related NAM, ATAF1/2 and CUC2 domain transcription factors (NACs) act as the first layer of master regulators of secondary wall biosynthesis; these are NST1 (NAC secondary wall thickening promoting factor 1), NST2 and NST3/ SND1 (secondary wall-associated NAC domain protein 1) (Mitsuda et al, 2005(Mitsuda et al, , 2007Zhong et al, 2006). Interestingly, the function of NAC master regulators is conserved in various plant species (Zhao et al, 2010;Wang et al, 2011;Lin et al, 2013;Valdivia et al, 2013;Grover et al, 2014). MYB domain transcription factors also serve as master regulators, but many operate downstream of the NACs Ko et al, 2009;McCarthy et al, 2009;Zhou et al, 2009;Bhargava et al, 2010).…”

Biofuel Potential of Plants Transformed Genetically with NAC Family Genes

“…The gene also gets induced by ABA and drought stresses ( He et al, 2005 ). In our laboratory, we have identified a cold-inducible NAC gene from a Brassicaceae family member Lepidium latifolium ( LlaNAC ), which was subsequently validated by over-expressing the gene in tobacco plants ( Grover et al, 2014 ). The popularity of the NAC gene as a tool to induce stress tolerance in plants by genetic engineering can well be assessed by overlooking the number of such reports within the calendar year 2015 ( Table 1 ).…”

“…In our laboratory, we raised LlaNAC over-expressor lines that could accumulate 2–3 times more biomass and chlorophyll pigments than the wild-types. In addition, these plants matured early, had shorter life cycles ( Grover et al, 2014 ), and could capture 3–5 times more carbon dioxide. It is pertinent to mention that the nearest homolog, ANAC056 from Arabidopsis thaliana , of the gene that we cloned (i.e., LlaNAC ) clustered with VND subfamily of genes ( Zhong et al, 2010a ).…”

“…Previous estimated have suggested that as many as 72 genes are the target genes to NAC proteins ( Shamimuzzaman and Vodkin, 2013 ). Such versatility in their action is partly due to their ability to form homo- and hetero-dimers, which act as transcriptional switches ( Olsen et al, 2005 ), and partly because many NAC TFs are downstream to each other ( Grover et al, 2014 ).…”

Physiological and biochemical plasticity of Lepidium latifolium as ‘sleeper weed’ in Western Himalayas

“…In India, L. latifolium is found in the cold‐arid zone of Ladakh Himalayas where it grows naturally at altitudes ranging from 2500 to 4500 m above sea level in parts of Jammu and Kashmir and Himachal Pradesh, and it is used as phytofood (Kaur et al ). Owing to its adaptive potential, many genes have recently been isolated from this plant (Gupta et al , Grover et al , Sinha et al ). We have also shown a very responsive redox mechanism in this ecotype of perennial pepperweed (Kaur et al ) wherein, glutathione plays an important role in induction of antioxidant enzymes with higher thiol content.…”