.

Plant geneticists at Rutgers, The State University of New Jersey, may have solved one of the fundamental problems in genetically engineered or modified (GM or GMO) crop agriculture: genes leaking into the environment.

In a recent paper published in the Proceedings of the National Academy of Science, Rutgers Professor Pal Maliga and research associate Zora Svab advocate an alternative and more secure means of introducing genetic material into a plant. In GM crops today, novel genes are inserted into a cell nucleus but can eventually wind up in pollen grains or seeds that make their way out into the environment.

The two researchers at Rutgers’ Waksman Institute of Microbiology argue for implanting the genes into another component of the cell – the plastid – where the risk of escape is minimized. Plastids, rarely found in pollen, are small bodies inside the cell that facilitate photosynthesis, the basic life process in plants.

“Our work with a tobacco plant model is breathing new life into an approach that had been dismissed out-of-hand for all the wrong reasons,” said Maliga. “Introducing new agriculturally useful genes through the plastid may prove the most effective means for engineering the next generation of GM crops.”

Skeptics had claimed that the approach was ineffective, based on 20-year-old genetic data showing that 2 percent of the pollen carried plastids. In the new study, Svab and Maliga found plastids in pollen 100- to 1000-times less frequently. This is well below the threshold generally accepted for additional containment measures.

The agricultural community worldwide seems to be embracing GM crops because the technology has the potential to deliver more healthful and nutritious crops, and increase crop yields with less use of chemical fertilizers and pesticides.

A “News Focus” story in the May 25 issue of the journal Science reported that genetically modified crops are flourishing worldwide, including in six European Union countries. “Last year (2006), 10 million farmers in 22 countries planted more than 100 million hectares with GM crops,” it said.

There has been serious opposition to genetically modified agriculture both in the United States and abroad, coming from concerns about “foreign genes” escaping from GM crops, crossing with and contaminating other crops and wild species, and disrupting the ecosystem.

Pursuing the approach elucidated and advocated by the Rutgers researchers’ findings may allay some of these fears and deflate the more vociferous arguments.

Svab and Maliga acknowledge that different strains of tobacco may produce plastid-carrying pollen at different frequencies, possibly accounting for some of the discrepancy between the old genetic data and the new. They emphasize that it will be important that any new crops that are developed be selected for low plastid pollen.

“We expect that there are nuclear genes which control the probability of plastids finding their way into pollen, but we have the tools that can be used to identify those genetic lines in every crop that will transmit plastids only at a low frequency,” Maliga said.

Source: Proceedings of the National Academy of Science

Exceptional transmission of plastids and mitochondria from the transplastomic pollen parent and its impact on transgene containment
Zora Svab, and Pal Maliga^*
Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854-8020
Edited by Maarten Koornneef, Wageningen University and Research Centre, Wageningen, The Netherlands, and approved February 28, 2007 (received for review January 4, 2007)

ABSTRACT

Plastids in Nicotiana tabacum are normally transmitted to the progeny by the maternal parent only. However, low-frequency paternal plastid transmission has been reported in crosses involving parents with an alien cytoplasm. Our objective was to determine whether paternal plastids are transmitted in crosses between parents with the normal cytoplasm. The transplastomic father lines carried a spectinomycin resistance (aadA) transgene incorporated in the plastid genome. The mother lines in the crosses were either (i) alloplasmic, with the Nicotiana undulata cytoplasm that confers cytoplasmic male sterility (CMS92) or (ii) normal, with the fertile N. tabacum cytoplasm. Here we report that plastids from the transplastomic father were transmitted in both cases at low (10^–4-10^–5) frequencies; therefore, rare paternal pollen transmission is not simply due to breakdown of normal controls caused by the alien cytoplasm. Furthermore, we have found that the entire plastid genome was transmitted by pollen rather than small plastid genome (ptDNA) fragments. Interestingly, the plants, which inherited paternal plastids, also carried paternal mitochondrial DNA, indicating cotransmission of plastids and mitochondria in the same pollen. The detection of rare paternal plastid transmission described here was facilitated by direct selection for the transplastomic spectinomycin resistance marker in tissue culture; therefore, recovery of rare paternal plastids in the germline is less likely to occur under field conditions.

Source: click HERE

The news item on this page is copyright by the organization where it originated - Fair use notice

Other news from this source