title: Strength, Stability, and cis-Motifs of In silico Identified Phloem-Specific Promoters in Brassica juncea (L.).
abstract: Aphids, a hemipteran group of insects pose a serious threat to many of the major crop species including Brassica oilseeds. Transgenic strategies for developing aphid-resistant plant types necessitate phloem-bound expression of the insecticidal genes. A few known phloem-specific promoters, in spite of tissue-specific activity fail to confer high level gene-expression. Here, we identified seven orthologues of phloem-specific promoters in B. juncea (Indian mustard), and experimentally validated their strength of expression in phloem exudates. Significant cis-motifs, globally occurring in phloem-specific promoters showed variable distribution frequencies in these putative phloem-specific promoters of B. juncea. In RT-qPCR based gene-expression study promoter of Glutamine synthetase 3A (GS3A) showed multifold higher activity compared to others, across the different growth stages of B. juncea plants. A statistical method employing four softwares was devised for rapidly analysing stability of the promoter-activities across the plant developmental stages. Different statistical softwares ranked these B. juncea promoters differently in terms of their stability in promoter-activity. Nevertheless, the consensus in output empirically suggested consistency in promoter-activity of the six B. juncea phloem- specific promoters including GS3A. The study identified suitable endogenous promoters for high level and consistent gene-expression in B. juncea phloem exudate. The study also demonstrated a rapid method of assessing species-specific strength and stability in expression of the endogenous promoters.
authors.affiliation: National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute Campus New Delhi, India.
authors.forename: Murali Krishna
authors.initials: MK
authors.lastname: Koramutla
authors.affiliation: National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute Campus New Delhi, India.
authors.forename: Deepa
authors.initials: D
authors.lastname: Bhatt
authors.affiliation: National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute Campus New Delhi, India.
authors.forename: Manisha
authors.initials: M
authors.lastname: Negi
authors.affiliation: Department of Biotechnology, Periyar University Salem, India.
authors.forename: Perumal
authors.initials: P
authors.lastname: Venkatachalam
authors.affiliation: National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute Campus New Delhi, India.
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Jain
authors.affiliation: National Research Centre on Plant Biotechnology, Indian Agricultural Research Institute Campus New Delhi, India.
authors.forename: Ramcharan
authors.initials: R
authors.lastname: Bhattacharya
keywords: aphid-resistance; phloem promoters; plant-promoters; promoter analysis; promoter elements; promoter stability; transgenic resistance