AUTHOR=Koramutla Murali Krishna , Bhatt Deepa , Negi Manisha , Venkatachalam Perumal , Jain Pradeep K. , Bhattacharya Ramcharan 

TITLE=Strength, Stability, and cis-Motifs of In silico Identified Phloem-Specific Promoters in Brassica juncea (L.)

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00457

DOI=10.3389/fpls.2016.00457

ISSN=1664-462X

ABSTRACT=<p>Aphids, a hemipteran group of insects pose a serious threat to many of the major crop species including <italic>Brassica</italic> 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 <italic>B. juncea</italic> (Indian mustard), and experimentally validated their strength of expression in phloem exudates. Significant <italic>cis</italic>-motifs, globally occurring in phloem-specific promoters showed variable distribution frequencies in these putative phloem-specific promoters of <italic>B. juncea</italic>. In RT-qPCR based gene-expression study promoter of <italic>Glutamine synthetase 3A (GS3A)</italic> showed multifold higher activity compared to others, across the different growth stages of <italic>B. juncea</italic> 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 <italic>B. juncea</italic> promoters differently in terms of their stability in promoter-activity. Nevertheless, the consensus in output empirically suggested consistency in promoter-activity of the six <italic>B. juncea</italic> phloem- specific promoters including GS3A. The study identified suitable endogenous promoters for high level and consistent gene-expression in <italic>B. juncea</italic> phloem exudate. The study also demonstrated a rapid method of assessing species-specific strength and stability in expression of the endogenous promoters.</p>