Artist’s depiction of several important crop plants in the grass family — the fifth largest family of plants with about 11,000 species, including wheat, corn, rice, sorghum, millet, sugarcane and bamboo. A massive new study clarifies the evolutionary relationships in the grass family tree and provides insight into the evolution of a type of photosynthesis — known as “C4 photosynthesis”—in grasses that allows the plants to harness the sun’s energy in hot, dry climates while conserving water. Credit: Yiyong Zhao
The evolutionary relationships among grasses—including important crop plants like wheat, rice, corn, and sugarcane—have been clarified in a new molecular study of the grass family tree. Having a clear picture of the relationships among the grasses can help understanding of how important crop traits like seed size or disease resistance evolves and eventually could inform manipulation of these traits to increase crop yields.
The massive study, which includes a sampling of over 350 grass species, also provides evidence that a type of photosynthesis—known as C4 photosynthesis—that allows the plants to harness the sun’s energy in hot, dry climates evolved independently multiple times within different grass lineages.
A paper describing the study by an international team of researchers led by Penn State scientists appears online in the journal Molecular Plant.
“The grasses are the fifth largest family of plants with about 11,000 species,” said Hong Ma, Dorothy Foehr Huck and J. Lloyd Huck Chair of Plant Reproductive Development and Evolution and professor of biology at Penn State and the leader of the research team. “These range from the grasses that make up your lawn to food crops that feed humans and their livestock to large woody species like bamboo, and, of course, many, many non-crop species. We collected specimens of a broad sampling of grasses from around the world to build the most comprehensive grass family tree to date using nuclear genes to better understand the evolutionary relationships among these important plants.”
The research team generated transcriptomes—DNA sequences of all of the genes expressed by an organism—for 342 grass species and whole-genome sequences for seven additional species. Combined with existing transcriptome and genome datasets for grasses, the research team compared gene sequences for a total of 357 species, including members of all 12 grass subfamilies and 231 different grass genera—the level of classification just above species.
Like animals, plant cells contain organelles called mitochondria that have a genome separate from what we generally think of as the cell’s genome found in its nucleus. Plant cells also have organelles called plastids—like chloroplasts, which perform photosynthesis— that also have separate genomes. Many previous studies of the grass family tree usually compared the plastid genomes, but for this study, the research team focused on the plant’s nuclear genome, which is larger and inherited from both plant parents.
“To build the grass family tree we compared the DNA sequence of about 1200 genes from the nuclear genomes of the grasses in our sample,” said Ma. “Using the larger nuclear genome, which is made feasible by recent advances in technology that have greatly reduced the time and cost of DNA sequencing, allowed us to make finer distinctions among grass species and resolve relationships that were previously difficult to interpret. We think the relationships among grasses we see in our study are very reliable, but we acknowledge that it is not perfect because we have analyzed only a small fraction of nuclear genes.”
Of the 12 grass subfamilies, the team confirmed that 11 were monophyletic—meaning that all of the members of the subfamily shared a single common ancestor in the past. For the 12th subfamily, the new study suggests that it might be better split into two separate subfamilies. Below the level of the subfamily, some tribes and even genera were also found to not be monophyletic. The study places the overall age of the grass family at about 101 million years using molecular clock estimates that measures time by tracking the number of changes or mutations in DNA sequences, while using fossils to date specific points in the grass history.
Having an accurate understanding of the relationships among species for any large group is vital for comparative and evolutionary studies of the group. To demonstrate this, the team looked at genes involved in C4 photosynthesis. C4 photosynthesis is a form of photosynthesis that uses a four-carbon intermediary molecule, in addition to a three-carbon molecule, which is usually used by C3 photosynthesis. This evolutionary novelty, which probably involves evolutionary changes in many tens of genes, allows plants like corn or millet that grow in hot, dry habitats to perform photosynthesis efficiently while conserving water.
“Our study shows that C4 photosynthesis has evolved from C3 independently several times in the grass family,” said Ma. “The evolutionary pathways leading to C4 photosynthesis differ in various lineages by using a different copy of a key enzyme or by having different changes in such a gene. So, if we want to understand C4 photosynthesis in a particular species, it is helpful to know how it is related to other species that use C4. This is true for other traits we might be interested in, and not just in crop species, but also for ecological studies or in model grass species used in laboratories.”
More information:
Weichen Huang et al, A well-supported nuclear phylogeny of Poaceae and implications for the evolution of C4 photosynthesis, Molecular Plant (2022). DOI: 10.1016/j.molp.2022.01.015
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A new molecular family tree of grasses (2022, March 2)
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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
