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PNAS Papers Describe Lateral Root Development in Rice, Ancient DNA Preserved in Sediment

Editor's Note: Some of the articles described below are not yet available at the PNAS site but are scheduled to be posted this week.

Using a variety of approaches including RNA sequencing and transcriptomic analysis, a group led by Nagoya University researchers has identified a family of genes involved in lateral root development in rice. The ability of plant root systems to proliferate within nutrient-rich patches of soil is key to stable crop production under variable environments, but the molecular mechanisms underlying this plasticity are not fully understood. As they report in a paper scheduled to be posted at the Proceedings of the National Academy of Sciences this week, the investigators find that two WUSCHEL-related homeobox transcription factors play a significant role in determining lateral root (LR) type in rice, having opposing effects on LR primordium size. "As the LR type determined by its primordium size is an important phenotypic trait for the growth maintenance of rice plants under variable water environments, our study provides important insights for improving plant resilience to environmental stresses through plastic root development," the study's authors write.

An analysis of ancient DNA collected over several decades from prehistoric sites across the world reveals that DNA can be reliably preserved in blocks of undisturbed sediment, according to a report in last week's Proceedings of the National Academy of Sciences. Ancient DNA recovered from sediments represents a rich resource for the study of past hominin and environmental diversity, but little is known about how DNA is preserved in sediments and the extent to which it may be translocated between archaeological strata. To investigate, a team led by scientists from the Max Planck Institute for Evolutionary Anthropology examined DNA preservation in 47 blocks of resin-impregnated archaeological sediment collected over the last four decades for micromorphological analyses at 13 prehistoric sites in Europe, Asia, Africa, and North America. They find that impregnated blocks of intact sediment are excellent archives of DNA. They write that DNA distribution is highly heterogeneous at the microscale in the cave sediment studied, "suggesting that post-depositional movement of DNA is unlikely to be a common phenomenon in cases where the stratigraphy is undisturbed." The researchers also propose a method for maximizing the yield of ancient DNA information from sediments: an initial screening of loose sediment samples from throughout a stratigraphic section to obtain broad spatial and temporal coverage of ancient DNA survival for the taxa of interest and to identify those parts of the stratigraphy of greatest potential for further sampling, followed by a targeted extraction of ancient DNA from identified microfeatures in impregnated blocks to increase the chance of recovering a high-yield sample of DNA.