Salt cress (Thellungiella halophila) is a small winter annual crucifer with a short life cycle. It has a small genome (about 2 × Arabidopsis) with high sequence identity (average 92%) with Arabidopsis, and can be genetically transformed by the simple floral dip procedure. It is capable of copious seed production. Salt cress is an extremophile native to harsh environments and can reproduce after exposure to extreme salinity (500 mm NaCl) or cold to −15°C. It is a typical halophyte that accumulates NaCl at controlled rates and also dramatic levels of Pro (>150 mm) during exposure to high salinity. Stomata of salt cress are distributed on the leaf surface at higher density, but are less open than the stomata of Arabidopsis and respond to salt stress by closing more tightly. Leaves of salt cress are more succulent-like, have a second layer of palisade mesophyll cells, and are frequently shed during extreme salt stress. Roots of salt cress develop both an extra endodermis and cortex cell layer compared to Arabidopsis. Salt cress, although salt and cold tolerant, is not exceptionally tolerant of soil desiccation. We have isolated several ethyl methanesulfonate mutants of salt cress that have reduced salinity tolerance, which provide evidence that salt tolerance in this halophyte can be significantly affected by individual genetic loci. Analysis of salt cress expressed sequence tags provides evidence for the presence of paralogs, missing in the Arabidopsis genome, and for genes with abiotic stress-relevant functions. Hybridizations of salt cress RNA targets to an Arabidopsis whole-genome oligonucleotide array indicate that commonly stress-associated transcripts are expressed at a noticeably higher level in unstressed salt cress plants and are induced rapidly under stress. Efficient transformation of salt cress allows for simple gene exchange between Arabidopsis and salt cress. In addition, the generation of T-DNA-tagged mutant collections of salt cress, already in progress, will open the door to a new era of forward and reverse genetic studies of extremophile plant biology.

Summary: Glycine betaine plays an important role in some plants, including maize, in conditions of abiotic stress, but different maize varieties vary in their capacity to accumulate glycine betaine. An elite maize inbred line DH4866 was transformed with the betA gene from Escherichia coli encoding choline dehydrogenase (EC 1.1.99.1), a key enzyme in the biosynthesis of glycine betaine from choline. The transgenic maize plants accumulated higher levels of glycine betaine and were more tolerant to drought stress than wild‐type plants (non‐transgenic) at germination and the young seedling stage. Most importantly, the grain yield of transgenic plants was significantly higher than that of wild‐type plants after drought treatment. The enhanced glycine betaine accumulation in transgenic maize provides greater protection of the integrity of the cell membrane and greater activity of enzymes compared with wild‐type plants in conditions of drought stress.

Chenopodium quinoa is a halophytic pseudocereal crop that is being cultivated in an ever-growing number of countries. Because quinoa is highly resistant to multiple abiotic stresses and its seed has a better nutritional value than any other major cereals, it is regarded as a future crop to ensure global food security. We generated a high-quality genome draft using an inbred line of the quinoa cultivar Real. The quinoa genome experienced one recent genome duplication about 4.3 million years ago, likely reflecting the genome fusion of two Chenopodium parents, in addition to the γ paleohexaploidization reported for most eudicots. The genome is highly repetitive (64.5% repeat content) and contains 54 438 protein-coding genes and 192 microRNA genes, with more than 99.3% having orthologous genes from glycophylic species. Stress tolerance in quinoa is associated with the expansion of genes involved in ion and nutrient transport, ABA homeostasis and signaling, and enhanced basal-level ABA responses. Epidermal salt bladder cells exhibit similar characteristics as trichomes, with a significantly higher expression of genes related to energy import and ABA biosynthesis compared with the leaf lamina. The quinoa genome sequence provides insights into its exceptional nutritional value and the evolution of halophytes, enabling the identification of genes involved in salinity tolerance, and providing the basis for molecular breeding in quinoa.

Broomcorn millet (Panicum miliaceum L.) is the most water-efficient cereal and one of the earliest domesticated plants. Here we report its high-quality, chromosome-scale genome assembly using a combination of short-read sequencing, single-molecule real-time sequencing, Hi-C, and a high-density genetic map. Phylogenetic analyses reveal two sets of homologous chromosomes that may have merged ~5.6 million years ago, both of which exhibit strong synteny with other grass species. Broomcorn millet contains 55,930 protein-coding genes and 339 microRNA genes. We find Paniceae-specific expansion in several subfamilies of the BTB (broad complex/tramtrack/bric-a-brac) subunit of ubiquitin E3 ligases, suggesting enhanced regulation of protein dynamics may have contributed to the evolution of broomcorn millet. In addition, we identify the coexistence of all three C₄ subtypes of carbon fixation candidate genes. The genome sequence is a valuable resource for breeders and will provide the foundation for studying the exceptional stress tolerance as well as C₄ biology.