Tag Archives: #flowering

Plant Flowering in Low-nitrogen Soils: A Mechanism Revealed (Botany)

Scientists from Japan, Europe and the USA have described  a pathway leading to the accelerated flowering of plants in low-nitrogen soils. These findings could eventually lead to increases in agricultural production.

Nitrogen is one of the three macronutrients required by plants for growth and development, along with phosphorus and potassium. Nitrogen-rich condition induces plant growth, particularly the growth of stems and leaves, while delaying flowering. On the other hand, in some plants, low-nitrogen conditions lead to a change from growth mode to reproductive mode, therefore accelerating flowering. However, the molecular mechanisms that regulate flowering under these conditions are not known.

A team of scientists led by Associate Professor Takeo Sato of Hokkaido University’s Graduate School of Life Science has revealed the molecular mechanism responsible for the acceleration of flowering in Arabidopsis under low nitrogen conditions. Their findings were published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Arabidopsis, a cruciferous plant, is well known as a model plant in biology and has an extensive database of its protein expression. In the current study,  the team first identified a set of proteins involved in flowering that became active as a result of changes in nitrogen level. One of these was the gene regulation factor FLOWERING BHLH 4 (FBH4). Through experiments using FBH4 deficient plants, this protein was found to be responsible for accelerated flowering under low-nitrogen conditions.

FBH4 is necessary for accelerated flowering in Arabidopsis. Accelerated flowering is only seen in the wild type(left), but not in FBH4 deficient plants (right) plants, under low-nitrogen conditions (Miho Sanagi, et al. Proceedings of the National Academy of Sciences of the United States of America. May 11, 2021).

Further investigation suggested that FBH4 is extensively phosphorylated by another protein called SnRK1. Low-nitrogen conditions suppress SnRK1 activity, which in turn results in the dephosphorylation of FBH4. The dephosphorylated FBH4 moves to the nucleus to activate genes responsible for flowering. Dephosphorylated FBH4 is also responsible for controlling the expression of other genes vital for plant survival under low nitrogen conditions, particularly those related to nitrogen recycling and remobilization.

The scientists concluded that, in response to inadequate nitrogen, Arabidopsis plants appear to precisely control gene expression related to developmental and metabolic processes required for flowering through FBH4. “The FBH family of genes is present in major crop plants,” says Takeo Sato. “Crop plants exhibit early flowering under low-nitrogen conditions; if we can control FBH activities in these crop plants, it might be an effective way to sustainably increase agricultural production.”

Takeo Sato, with Arabidopsis plants in the culture room (Photo: Takeo Sato).

Original Article:

Miho Sanagi, et al. Low nitrogen conditions accelerate flowering by modulating the phosphorylation state of FLOWERING BHLH 4 in ArabidopsisProceedings of the National Academy of Sciences of the United States of America. May 11, 2021. DOI: 10.1073/pnas.2022942118


This work was supported by Grants-in-Aid for Scientific Research (17K08190, 20K05949, 26292188, 18H02162) and Research Fellowships for Young Scientists from the Japan Society for the Promotion of Science (JSPS), the Northern Advancement Center for Science & Technology (NOASTEC) foundation, the Hokkaido University Young Scientist Support Program, the National Institutes of Health (R01GM079712), the National Science Foundation (IOS-1656076), Next-Generation BioGreen 21 Program (PJ013386) from the Rural Development Administration, Republic of Korea, and the Max Planck Society.

Featured image: Arabidopsis plants used in one of the experiments during the study (Photo: Takeo Sato).

Provided by Hokkaido University

Discovery of Flowering Gene in Cacao May Lead To Accelerated Breeding Strategies (Agriculture)

For the first time, Penn State researchers have identified a gene that controls flowering in cacao, a discovery that may help accelerate breeding efforts aimed at improving the disease-ridden plant, they suggested.

Characterizing the Flowering Locus T gene in cacao, responsible for the production of florigen — a protein that triggers flowering in most plants — is important, according to study co-author Mark Guiltinan, J. Franklin Styer Professor of Horticultural Botany and professor of plant molecular biology. He expects this advancement to enable scientists to develop disease-resistant trees faster, which is critical because 20% to 30% of the world’s cacao crop is lost to disease annually.

“Breeding tree crops like cacao is very slow and can take 20 or more years to release a new variety,” he said. “Knowledge of the mechanisms of flowering may lead to methods to accelerate cacao breeding and to develop trees that produce fruit sooner than conventional varieties, which takes two to four years. Each year we move closer to these goals as we continue to explore the molecular biology of the cacao tree.”

To find the flowering gene in cacao, lead researcher Sarah Prewitt, doctoral candidate in plant science in the College of Agricultural Sciences, first looked at genes known to be responsible for flowering in the Arabidopsis plant, the genome of which has been studied widely for decades. Before finding the cacao flowering gene, she tested an Arabidopsis flowering gene in cacao to see how the plant developed.

Testing her theory, she overexpressed that gene to trigger very early flowering in cacao “plantlets” in the lab and showed that those tiny flowers produced grains of pollen that were viable.

“To find the flowering gene in cacao, we used a bioinformatics approach, taking the sequence of the gene from Arabidopsis and looking for similar genes in the cacao genome,” Prewitt said. “I found the cacao gene that promotes flowering because the sequences look very similar.”

The fungal disease black pod rot, shown here in cacao seed pods, is a serious problem in all areas of the world where the crop is grown. Caused by the fungus Phytophthora, black pod rot causes pod losses of up to 30% and kills as many as 10% of the trees annually. Researchers hope to breed disease-resistant trees, and finding the cacao flowering gene promises to speed up their efforts. © PlantVillage, Penn State

Geneticists consider the function of the florigen flowering gene to be “highly conserved,” Prewitt added. “That means the gene is extremely consistent — it does what it does in every plant genome that you look in,” she said. “The florigen flowering gene certainly has been looked at in a lot of plants, and it’s very reliable. It controls the timing of flowering.”

In findings published May 15 in BMC Plant Biology, the researchers reported on the role of cacao’s single flowering gene, Flowering Locus T, demonstrated by gene-expression analysis. They also documented the results of their introduction of the flowering gene from Arabidopsis into cacao. Overexpressing that gene resulted in “precocious” flowering in cacao tissue culture, they explained, which demonstrated the extremely similar function of florigen genes and the mechanisms that control flowering in both Arabidopsis and cacao.

While intriguing on a scientific level, the discovery of the cacao Flowering Locus T gene could have a potentially significant, real-world impact, Guiltinan noted, by helping to improve the lives of millions of cacao farmers in developing countries sooner than previously thought possible. He pointed out that the breeding of cacao varieties with high yields, disease resistance, resilience to climate change and desirable quality traits is an important component of a broader goal to develop sustainable farming systems for cacao.

“Better cacao varieties can increase the income, and thus the well-being, of cacao farmers who live in some of the most impoverished regions of the world, such as West Africa,” he said. “In turn, this will benefit the economies of these countries and the environment and will provide a sustainable source of the main raw ingredient for the chocolate industry.”

Also involved in the research were Siela Maximova, research professor of plant biotechnology, and Akiva Shalit-Kaneh, postdoctoral scholar in plant science.

Penn State’s College of Agricultural Sciences, the Huck Institutes of the Life Sciences, the Penn State Endowed Program in the Molecular Biology of Cacao and the U.S. Department of Agriculture’s National Institute of Food and Agriculture supported this work.

Featured image: In the research, embryonic cacao, over expressing the florigen gene, develop tiny flowers in tissue culture. This study is significant because cacao trees typically don’t flower until they are between three and eight years of age. Such early flowering promises to greatly speed up breeding to develop disease-resistant trees. © Sarah Prewitt, Penn State

Reference: Prewitt, S.F., Shalit-Kaneh, A., Maximova, S.N. et al. Inter-species functional compatibility of the Theobroma cacao and Arabidopsis FT orthologs: 90 million years of functional conservation of meristem identity genes. BMC Plant Biol 21, 218 (2021). https://doi.org/10.1186/s12870-021-02982-y

Provided by Penn State

New Species of Mustard Family of Flowering Plants Found in Hengduan Mountains (Botany)

Rorippa is a cosmopolitan weed genus in the Brassicaceae, the mustard family of flowering plants. It is a large genus of chiefly weedy aquatic or marsh herbs that have pinnate or pinnatifid leaves, yellow flowers, and terete pods with seeds in two rows in each cell. 

In a revision of the Rorippa genus in the Pan-Himalaya region, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences recognized five species from the Hengduan Mountains, including R. globosa with globose fruit, and the other four, R. dubiaR. elataR. indica, and R. palustris  with oblong or linear silique. 

In field works during 2017–2020, the researchers collected some materials of unknown Rorippa plants. After conducting morphological characterization and phylogenetic analysis, they confirmed that the plant is new to science. They named it as Rorippa hengduanshanensis to reflect its geographic distribution, the Hengduan Mountains. Relevant results were published in Phytotaxa.

Rorippa hengduanshanensis A. Habitat; B. Inflorescence; C. Fruits; D. E. F. Morphology and transection of R. hengduanshanensis, R. dubia, and R. indica fruits, respectively; G. Arrangement of seeds; H. Seeds. (Image by ZHENG Quanjing)

Rorippa hengduanshanensis has lateral lobed leaves, four petals, and divaricate pedicels, which mostly resemble R. dubia and R. indica. It differs from R. benghalensis in the ebracteate racemes; from R. dubia in the flattened silique, the presence of four petals and the ploidy level; and from R. indica in the uniseriate seeds. 

R. hengduanshanensis is endemic in Yunnan, and Sichuan provinces of China. Ittypically grows in moist habitats, roadsides, field margins, gardens, or riverbanks at altitudes of 1,500 to 3,000 meters.

Fruits of Rorippa hengduanshanensis (Image by ZHENG Quanjing)

Since the species appears to only distribute in high-altitude regions, which is potentially threatened by global climate change, the researchers proposed its conservation status as nearly threatened. 

Featured image: Flowers of Rorippa hengduanshanensis (Image by ZHENG Quanjing)

Reference: QUAN-JING ZHENG, CHIH-CHIEH YU, YAO-WU XING, TING-SHEN HAN, “A new Rorippa species (Brassicaceae), R. hengduanshanensis, from the Hengduan Mountains in China”, Phytotaxa, 480(3), 2021. https://www.biotaxa.org/Phytotaxa/article/view/phytotaxa.480.3.1

Provided by Chinese Academy of Sciences