Triticeae Cereals

The Triticeae CBF Gene Cluster-To Frost Resistance and Beyond

The pivotal role of CBF/DREB1 transcriptional factors in Triticeae crops involved in the abiotic stress response has been highlighted. The CBFs represent an important hub in the ICE-CBF-COR pathway, which is one of the most relevant mechanisms capable of activating the adaptive response to cold and drought in wheat, barley, and rye. Understanding the intricate mechanisms and regulation of the cluster of CBF genes harbored by the homoeologous chromosome group 5 entails significant potential for the genetic improvement of small grain cereals. Triticeae crops seem to share common mechanisms characterized, however, by some peculiar aspects of the response to stress, highlighting a combined landscape of single-nucleotide variants and copy number variation involving CBF members of subgroup IV. Moreover, while chromosome 5 ploidy appears to confer species-specific levels of resistance, an important involvement of the ICE factor might explain the greater tolerance of rye. By unraveling the genetic basis of abiotic stress tolerance, researchers can develop resilient varieties better equipped to withstand extreme environmental conditions. Hence, advancing our knowledge of CBFs and their interactions represents a promising avenue for improving crop resilience and food security.

Barley (Hordeum vulgare L.) transformation using immature embryos

Barley is a major crop species, and also has become a genetic model for the small grain temperate cereals. A draft barley genome sequence has recently been completed, opening many opportunities for candidate gene isolation and functionality testing. Thanks to the development of customizable endonucleases, also site-directed genome modification recently became feasible for higher plants, which marks the beginning of a new era of genetic engineering. The development of improved binary vectors and hypervirulent Agrobacterium tumefaciens strains has raised the efficiency of genetic transformation in barley to a level where the technique has become relatively routine. The transformation method described here involves immature barley embryos cocultivated with Agrobacterium after removal of their embryo axis. Critical adjustments to the protocol have included the supplementation of the cocultivation medium with the polyphenolic signaling compound acetosyringone at comparatively high concentration and the use of cysteine to reduce the extent of cellular oxidation upon agroinfection. In addition, the use of liquid, rather than solid, cocultivation medium promotes the throughput of the method. The protocol has delivered well over 10,000 transgenic barley plants over the past 10 years. Routine transformation efficiency, calculated on the basis of the recovery of independent transgenics per 100 explants, has reached about 25 % in cultivar (cv.) "Golden Promise". The protocol has proven effective for more than 20 barley cultivars, although some adjustments to the culture conditions have had to be made in some cases. The transformation efficiency of cv. "Golden Promise" remains higher than that of any other cultivar tested.