Genotyping by Sequencing Reveals Genetic Relatedness of Southwestern U.S. Blue Maize Landraces

Diploid chromosome-level reference genome and population genomic analyses provide insights into Gypenoside biosynthesis and demographic evolution of Gynostemma pentaphyllum (Cucurbitaceae)

Gynostemma pentaphyllum (Thunb.) Makino is a perennial creeping herbaceous plant in the family Cucurbitaceae, which has great medicinal value and commercial potential, but urgent conservation efforts are needed due to the gradual decreases and fragmented distribution of its wild populations. Here, we report the high-quality diploid chromosome-level genome of G. pentaphyllum obtained using a combination of next-generation sequencing short reads, Nanopore long reads, and Hi-C sequencing technologies. The genome is anchored to 11 pseudo-chromosomes with a total size of 608.95 Mb and 26 588 predicted genes. Comparative genomic analyses indicate that G. pentaphyllum is estimated to have diverged from Momordica charantia 60.7 million years ago, with no recent whole-genome duplication event. Genomic population analyses based on genotyping-by-sequencing and ecological niche analyses indicated low genetic diversity but a strong population structure within the species, which could classify 32 G. pentaphyllum populations into three geographical groups shaped jointly by geographic and climate factors. Furthermore, comparative transcriptome analyses showed that the genes encoding enzyme involved in gypenoside biosynthesis had higher expression levels in the leaves and tendrils. Overall, the findings obtained in this study provide an effective molecular basis for further studies of demographic genetics, ecological adaption, and systematic evolution in Cucurbitaceae species, as well as contributing to molecular breeding, and the biosynthesis and biotransformation of gypenoside.

Biotechnological Advances to Improve Abiotic Stress Tolerance in Crops

The major challenges that agriculture is facing in the twenty-first century are increasing droughts, water scarcity, flooding, poorer soils, and extreme temperatures due to climate change. However, most crops are not tolerant to extreme climatic environments. The aim in the near future, in a world with hunger and an increasing population, is to breed and/or engineer crops to tolerate abiotic stress with a higher yield. Some crop varieties display a certain degree of tolerance, which has been exploited by plant breeders to develop varieties that thrive under stress conditions. Moreover, a long list of genes involved in abiotic stress tolerance have been identified and characterized by molecular techniques and overexpressed individually in plant transformation experiments. Nevertheless, stress tolerance phenotypes are polygenetic traits, which current genomic tools are dissecting to exploit their use by accelerating genetic introgression using molecular markers or site-directed mutagenesis such as CRISPR-Cas9. In this review, we describe plant mechanisms to sense and tolerate adverse climate conditions and examine and discuss classic and new molecular tools to select and improve abiotic stress tolerance in major crops.