Arabidopsis discoveries at the PRL

Over the MSU-DOE Plant Research Laboratory’s 60-year history, amazing discoveries have been made across many disciplines of molecular biology with photosynthetic organisms.

Arabidopsis thaliana is a model organism used by plant scientists to better understand the inner mechanisms of plants. When Arabidopsis emerged as serious genetic model organism in the 80s, Shauna and Chris Somerville were some of the first scientists to adopt it for plant physiological and biochemical studies and heavily contributed to the building of the Arabidopsis community. The first International Arabidopsis meeting in the United States and the third overall was organized by the Somerville’s at MSU in 1987. Eventually, many PRL faculty or scientists moving through their labs worked on Arabidopsis and spread the basic knowledge of how to explore this model plant throughout the world.

Arabidopsis was the first plant to have its genome decoded, leading to many important discoveries in plant biology, with uses in agriculture, human health, and more. Highlighted here are some of the achievements of PRL researchers in the field of Arabidopsis research.

A mutant lacking a specific chloroplast lipid – 1985

John Browse, Peter McCourt and Chris Somerville pioneered the “brute force” biochemical screening of fatty acid mutants using gas chromatography of fatty acid methylesters prepared directly from Arabidopsis leaves. The goal was to determine the role of glycerolipid acyl group desaturation in the cold tolerance of plants and to identify the underlying fatty acid desaturases.

A mutant with altered chloroplast lipid metabolism – 1988

Glycerolipids of the thylakoid membrane are assembled in many plants directly in the chloroplast and by the ER. Ljerka Kunst, John Browse and Chris Somerville discovered a mutant that disrupts the chloroplast pathway of thylakoid lipid assembly but still can survive by utilizing just the ER pathway like most grasses and legumes do naturally.

A mutant disrupting the ethylene hormone receptor – 1988

PRL researchers Tony Bleeker, Hans Kende, Mark Estelle and Chris Somerville discovered a mutant of Arabidopsis that does not respond to ethylene like their wild-type counterparts do. This led Tony Bleeker to find the first known plant hormone receptor, ETR1.

A beta amylase mutant with deficiency in starch metabolism – 1989

Tim Caspar, Chris Somerville, Jack Preiss, an MSU colleague in the Department of Biochemistry and Molecular Biology and his colleagues isolated starch deficient mutants. They used a biochemical approach by staining Arabidopsis leaves from a mutant population for the presence of starch and determined the underlying biochemistry of starch metabolism in plants.

Herbicide Resistant mutants – 1990

With the goal to develop selection markers for the genetic transformation of Arabidopsis, George Haughn and Chris Somerville isolated herbicide resistant mutants. In the process, they identified herbicide targets in amino acid biosynthesis that later led to the development of herbicide resistant crop plants.

A mutant defective in the phenol propanoid pathway – 1992

Clint Chapple, Chris Somerville and colleagues developed a mutant screen targeting the phenolpropanoid pathway based on the accumulation of fluorescent intermediates of the pathway in the mutants. Phenolpropanoids give rise to flower pigments and also provide the precursors for lignin, one of the key plant cell wall and wood components.

First map-based cloning of an Arabidopsis gene – 1992

Vicent Arondel, Bertrand Lemieux, Sue Gibson in Chris Somerville’s group at the PRL and Harvard Medical School collaborators Inhwan Hwang and Howard Goodman succeeded in the map-based cloning of an Arabidopsis gene encoding a fatty acid desaturase involved in the biosynthesis of omega 3 fatty acids. This work showed the feasibility of mapping a mutation to the defective gene in Arabidopsis, thereby identifying the causative gene for the mutant phenotype. Furthermore, the discovery of this particular gene led to the engineering of crops with an increased amount of omega-3s, which is beneficial for human health, leading to a decreased risk for cardiovascular disease, some forms of cancer, Alzheimer's disease, dementia and more.

Gibberellin mutants and Arabidopsis flowering – 1992

Ruth Wilson, John Heckman and Chris Somerville applied Arabidopsis genetics to explore the function of the plant growth hormone gibberellin in Arabidopsis.

Altered growth and cell walls in a fucose deficient mutant – 1993

A biochemical screening procedure was developed to identify mutants of Arabidopsis thaliana in which the polysaccharide composition of the cell wall was altered.

Large Scale sequencing of Arabidopsis cDNA clones – 1994

Sequencing of the transcriptome of a plant, which is the sum of all active genes providing a picture of the genome’s genetic activity in specific tissues or under specific environmental conditions, has nowadays become routine. In a collaborative effort by all PRL members, this method was pioneered for Arabidopsis at the PRL in 1994.

Abscisic acid mutants – 1997

Steve Schwartz, Karen Léon-Kloosterziel, Marteen Koornneef and Jan Zeevaart determined the key biochemical defect in mutants of Arabidopsis unable to produce the plant growth regulator abscisic acid.

Arabidopsis Xyloglucan fucosyltransferase – 1999

Natasha Raikhel, Ken Keegstra and their colleagues identified the Arabidopsis gene encoding a key enzyme of xyloglucan biosynthesis based on the orthologous protein purified from pea epicotyls.

Isolating protein import-competent Arabidopsis chloroplasts – 2001

Linda Fitzpatrick and Ken Keegstra demonstrated the isolation of protein import competent chloroplasts from Arabidopsis which, in combination with the respective mutants, enabled a detailed functional analysis of the chloroplast protein import machinery in plants.

Identification of Arabidopsis unstable transcripts – 2002

Rodrigo Guiterrez, Pam Green and colleagues identified on a genome-wide scale instable RNA transcripts as one means plants have to control gene expression.

Resad More: https://pubmed.ncbi.nlm.nih.gov/12167669/

The Arabidopsis Proteome – 2004

Rodrigo Guiterrez, Pam Green, Ken Keegstra and John Ohlrogge studied the proteome of Arabidopsis and identified thousands of genes specific to the plant linages.

Mutants deficient in Xyloglucan Biosynthesis – 2008

A multi-investigator collaborative effort at the PRL led by Ken Keegstra isolated a double mutant disrupted in xyloglucan biosynthesis. The plants lacked a major primary cell component and had a fragile cell wall.

Understanding how plants beat the heat – 2008

In a collaborative effort between the PRL and other MSU researchers an Arabidopsis transcription factor called bZIP28 was identified which is activated in the plant when the plant experiences heat stress. Understanding how bZIP28 works has allowed scientists to better know how plants respond to heat. This is especially important under our changing environmental conditions, where global temperatures continue to rise.

Gene regulatory networks controlling cold acclimation – 2002

Sarah Fowler and Mike Thomashow used emerging transcriptome profiling technology to demonstrate that cold acclimation in Arabidopsis involves multiple regulatory pathways in addition to the previously characterized CBF (C-repeat Binding Factor) cold response pathway. The work established that freezing tolerance in plants depends on distinct sets of cold-responsive genes.

Stomatal-based immunity – 2006

Research from Sheng Yang He’s lab showed that stomatal closure is an active plant innate immune response that restricts bacterial invasion. This discovery opened up the new field of stomatal-based immunity and overturned the long-held assumption that stomata serve as passive ports of bacterial entry.

Identification of the missing link in the jasmonate signaling pathway – 2007

Collaborative work between PRL alumni John Browse, Sheng Yang He and Gregg Howe led to the identification of the JAZ transcriptional repressor proteins. This research revealed the long-sought molecular mechanism by which plants respond to jasmonate hormones, which are critical for plant reproduction and defense against herbivores and pathogens.

CAMTA transcription factors control cold-regulated gene expression – 2009

In building on Mike Thomashow’s pioneering work on plant freezing tolerance, Colleen Doherty and others in the Thomashow group discovered that CAMTA (Calmodulin-binding Transcription Activator) transcription factors in Arabidopsis function as key regulators of cold-responsive gene expression and freezing tolerance.

Structure of the jasmonate receptor – 2010

Collaborative research between Ning Zheng and John Browse, together with Gregg Howe and Sheng Yang He in the PRL, elucidated the structure of the COI1-JAZ co-receptor for the bioactive ligand JA-Ile. This atomic-level view of the jasmonate receptor extended the concept that some plant hormones act as “molecular glue” to promote interactions between proteins.

Into the Future

PRL researchers are continuously making ground-breaking discoveries that help us understand the plants we rely on. We are looking into the future, not only on Earth but in the stars.

In 2023, Federica Brandizzi sent Arabidopsis seeds into space on the Artemis I mission. The seeds experienced conditions that humans have yet to face while on the transport ship, which flew farther than any other spacecraft with people aboard.

If humanity is to traverse the stars, we will need to feed ourselves. At present, little is known about how plants will grow away from Earth. This experiment is looking at the effects of spaceflight on the amino acids of the plants to see if growing healthier plants in space is sustainable.

While these results are still pending, it will be another step toward growing food off Earth, and Arabidopsis remains an important organism in making discoveries that will propel us into the future.

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Arabidopsis discoveries at the PRL