Ice-Binding Proteins Confer Freezing Tolerance in Arabidopsis

Lolium perenne is a freeze-tolerant ryegrass capable of withstanding extremely low temperatures. Ice-binding proteins (IBPs) are hypothesized to help the plant prevent freezing damage by restricting the growth of ice crystals in the apoplast. Melissa Bredow, together with her colleagues from Queen's University in Canada, investigated the expression, localization and freezing protection capabilities of two L. perenne IBP isoforms, LpIRI2 and LpIRI3, as well as a processed IBP (LpAFP).

All IBPs were expressed individually in Arabidopsis plants and were studied. Analysis showed that LpIRI2 and LpIRI3 were both upregulated following cold acclimation. Both the LpIRI3 and LpIRI2 isoforms also accumulate in the apoplast of transgenic Arabidopsis plants. Meanwhile, the processed isoform, LpAFP, remained intracellular.

Transgenic plants expressing either LpIRI2 or LpIRI3 showed reduced ion leakage after low-temperature treatments and had improved freezing survival while transgenic LpAFP-expressing lines did not exhibit any freezing protection. Freeze protection was also further enhanced by with the introduction of more than one IBP isoform.

These results demonstrate that apoplastic expression of L. perenne IBP isoforms could provide freezing protection to crops. Expression of more than one IBP also enhanced freezing protection.

For more on this study, read the article in Plant Biotechnology Journal.