Fertility restorer Indian mustard

The Indian mustard (Brassica juncea) was modified for restoring male fertility and herbicide tolerance. For male fertility restoration, the mustard expresses Bacillus amyloliquefaciens barstar, a protein inhibitor of barnase, in the tapetum cell layer of the pollen sac during anther development. Barnase is an RNase, which degrades RNA in the pollen and prevents the pollen from developing. With barstar expression, the RNase is inhibited and the pollen develops normally. Thus, crossing barstar expressing lines with barnase expressing (male sterile) lines restores male fertility in the progeny.

For glufosinate tolerance, the mustard expresses Streptomyces hygroscopicus phosphinothricin N-acetyltransferase, which inactivates the herbicide through acetylation.

To achieve the fertility restorer line EH-2 modbs 2.99 for hybrid seed production, the mustard variety Varuna was initially transformed with transgenic construct and then backcrossed into variety EH-2. Six backcrossings were performed to try to remove integration of vector backbone sequence.

Varuna (T-59) is extensively cultivated in northern India. EH-2 was developed from east European material by University of Nagpur.

pPZP200

The modified mustard contains two gene cassettes: Streptomyces hygroscopicus (bar) and Bacillus amyloliquefaciens barstar.

The bar coding sequence is under control of the Cauliflower mosaic virus (CaMV) enhanced 35S promoter and Rhizobium radiobacter octopine synthase terminator.

Barstar is under control of a Nicotiana tabacum TA29 pollen specific promoter and a CaMV 35S terminator. The TA29 promoter is active only in the tapetum cell layer of the pollen sac during anther development (male-specific expression). The coding sequence was codon optimized for expression in plants.

Note:
- Southern blot and segregation analyses indicated that the genome contains a single insertion
- DNA sequence analysis indicated that the insertion occurred in the 'B' genome.