USDA

The genetics behind the alternating sexes of walnut trees has been revealed by biologists at the University of California, Davis. The research, published Jan. 3 in Science, reveals a mechanism that has been stable in walnuts and their ancestors going back 40 million years — and which has some parallels to sex determination in humans and other animals.

Each year, nearly 30 million Americans purchase a real tree for the holidays. Growing the perfect Christmas tree takes about seven years, during which farmers need to keep insects, fungal pathogens and hungry deer at bay. While researchers suspect the distinctive piney smell the trees emit plays a role in deterring these pests, not all trees smell the same, and which chemical blends confer resistance is unclear. 

The development of maternal egg cells is pivotal for survival – but also precarious. During meiosis, the DNA-containing chromosomes can easily be broken or lost, causing infertility, miscarriage, or genetic disorders. Scientists have struggled to study these crucial cellular events in humans and other mammals.

Rice is a staple food crop for more than half the world’s population, but most farmers don’t grow high-yielding varieties because the seeds are too expensive. Researchers from the University of California’s Davis and Berkeley campuses have identified a potential solution: activating two genes in rice egg cells that trigger their development into embryos without the need for fertilization, which would efficiently create high-yielding clonal strains of rice and other crops.

Plants need to be able to communicate with themselves—by sending signals from their leaves to their roots to their flowers—so that they can coordinate growth and optimize resource use. They also need to communicate with other plants and organisms, which they achieve by releasing volatile organic compounds (VOCs), tiny molecules that are often associated with distinct smells. Scientists know a lot about how plants emit these odorous signals, however very little is known about how they receive and interpret them.

Maize is one of the world’s most widely grown crops. It is used for both human and animal foods and holds great cultural significance, especially for indigenous peoples in the Americas. Yet despite its importance, the origins of the grain have been hotly debated for more than a century. Now new research, published Dec. 1 in Science, shows that all modern maize descends from a hybrid created just over 5000 years ago in central Mexico, thousands of years after the plant was first domesticated.

Sunflowers famously turn their faces to follow the sun as it crosses the sky. But how do sunflowers “see” the sun to follow it? New work from plant biologists at the University of California, Davis, published Oct. 31 in PLOS Biology, shows that they use a different, novel mechanism from that previously thought.

“This was a total surprise for us,” said Stacey Harmer, professor of plant biology at UC Davis and senior author on the paper.

Scientists have long known that chloroplasts help plants turn the sun’s energy into food, but a new study, led by researchers in the Department of Plant Biology, shows that they’re also essential for plant immunity to viral and bacterial pathogens.

Chloroplasts are generally spherical, but a small percentage of them change their shape and send out tube-like projections called “stromules.” First observed over a century ago, the biological function of stromules has remained enigmatic.

An internal circadian clock controls the distinctive concentric rings of flowering in sunflowers, maximizing visits from pollinators, a new study from plant biologists at the University of California, Davis, shows. The work was published Jan. 13 in eLife.

A sunflower head is made up of hundreds of tiny florets. Because of the way sunflowers grow, the youngest florets are in the center of the flower face and the most mature at the edges, forming a distinctive spiral pattern from the center to the edge.