title: Targeted silencing of BjMYB28 transcription factor gene directs development of low glucosinolate lines in oilseed Brassica juncea.
abstract: Brassica juncea (Indian mustard), a globally important oilseed crop, contains relatively high amount of seed glucosinolates ranging from 80 to 120 μmol/g dry weight (DW). One of the major breeding objectives in oilseed Brassicas is to improve the seed-meal quality through the development of low-seed-glucosinolate lines (<30 μmol/g DW), as high amounts of certain seed glucosinolates are known to be anti-nutritional and reduce the meal palatability. Here, we report the development of transgenic B. juncea lines having seed glucosinolates as low as 11.26 μmol/g DW, through RNAi-based targeted suppression of BjMYB28, a R2R3-MYB transcription factor family gene involved in aliphatic glucosinolate biosynthesis. Targeted silencing of BjMYB28 homologs provided significant reduction in the anti-nutritional aliphatic glucosinolates fractions, without altering the desirable nonaliphatic glucosinolate pool, both in leaves and seeds of transgenic plants. Molecular characterization of single-copy, low glucosinolate homozygous lines confirmed significant down-regulation of BjMYB28 homologs vis-à-vis enhanced accumulation of BjMYB28-specific siRNA pool. Consequently, these low glucosinolate lines also showed significant suppression of genes involved in aliphatic glucosinolate biosynthesis. The low glucosinolate trait was stable in subsequent generations of the transgenic lines with no visible off-target effects on plant growth and development. Various seed quality parameters including fatty acid composition, oil content, protein content and seed weight of the low glucosinolate lines also remained unaltered, when tested under containment conditions in the field. Our results indicate that targeted silencing of a key glucosinolate transcriptional regulator MYB28 has huge potential for reducing the glucosinolates content and improving the seed-meal quality of oilseed Brassica crops.
authors.affiliation: National Institute of Plant Genome Research (NIPGR), New Delhi, India.
authors.forename: Rehna
authors.initials: R
authors.lastname: Augustine
authors.forename: Arundhati
authors.initials: A
authors.lastname: Mukhopadhyay
authors.forename: Naveen C
authors.initials: NC
authors.lastname: Bisht
mesh_terms: D002851:Chromatography, High Pressure Liquid; D020868:Gene Silencing; D005961:Glucosinolates / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009149:Mustard Plant / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics
chemical_list: D005961:Glucosinolates; D010940:Plant Proteins; D014157:Transcription Factors
keywords: Brassica juncea; MYB28; RNAi suppression; glucosinolates; secondary metabolites; transgenic plants