Amazing models plant — Arabidopsis thaliana

The selection and utilization of model plants are of great significance for genetic analysis, gene cloning and functional research. Arabidopsis thaliana has become the most dazzling star in the field of plant research in the past 40 years due to its small plant, abundant fruit, short life cycle, simple genome and simple genetic operation.

Arabidopsis, rapeseed, radish, and cabbage belong to the cruciferous family and are subdivided downward into the genus Ratella. Arabidopsis is also known as Rat-ear mustard, Arabidopsis, Arabidopsis, Latin name Arabidopsis thaliala (L.) Heynh. Arabidopsis thaliana is a herb widely distributed in Eurasia and northwest Africa.

Arabidopsis thaliana extract contains a variety of skin-friendly active ingredients, with antioxidant effect, can promote skin self-renewal and repair, effectively delay skin aging.

Arabidopsis used to be a silent, little-known blade of grass. Arabidopsis thaliana is neither tasty nor good-looking and has no economic value to humans. However, with the vigorous development of biology and classical genetics in the past 100 years, scientists have gradually noticed its research value.

Scientists have long hoped to find plants that reproduce as quickly as the animal equivalent of Drosophila melanogaster, which is easy to grow in a laboratory and suitable for genetic manipulation, thus fundamentally changing the long-term backwater in plant genetics.

Arabidopsis thaliana plants are small (4-10 plants can be grown in an 8cm square culture pot), have a short growth cycle (4-6 weeks from germination to flowering), and bear a lot of fruit (thousands of seeds can be produced per plant).

Arabidopsis thaliana has distinct morphological characteristics (FIG. 1). Rosette leaves are planted at the base of the plant and are obovate or spoon-shaped. Cauline leaves sessile, needle-shaped, or linear. Lateral branches are born at the base of leaf axils, the main stem, and the top of the lateral branches are born with racemes, four white spatulate petals, four strong stamens. Elongate, 1-1.5cm long, each pod can bear 50-60 seeds.

FIG. 1 Morphology of Arabidopsis thaliana
FIG. 1 Morphology of Arabidopsis thaliana

These characteristics make it easy to observe the mutant phenotype of Arabidopsis thaliana and provide convenience for mutant screening. Arabidopsis thaliana is a typical self-propagating plant, which is easy to maintain genetic stability. At the same time, artificial hybridization can be carried out conveniently, which is beneficial to genetic research.

Another advantage of Arabidopsis is that it is easy to convert. With constant practice, the floral tip has become the most common way of transforming Arabidopsis thaliana. The moss-extracted arabidopsis thaliana at 5-6 weeks of growth was capitalized to promote the growth of side branches (FIG. 2A). When the inflorescences were produced in large numbers, they were immersed in agrobacterium solution containing silwet and sucrose for several minutes (FIG. 2B). After 3-4 weeks, the transformed plants were seeded (FIG. 2C). Seeds were screened on plates containing suitable antibiotics, and healthy seedlings were transgenic (FIG. 2D).

This transformation method does not require tissue culture and plant regeneration, and is easy to operate and efficient, which provides convenience for researchers to establish mutant libraries, change the expression characteristics of target genes, and carry out complementary verification experiments.

FIG. 2 Transformation process of Arabidopsis thaliana (immersion)
FIG. 2 Transformation process of Arabidopsis thaliana (immersion)

The Arabidopsis genome is small and consists of five pairs of chromosomes. Its genome was sequenced by the International Arabidopsis Genome Consortium in 2000, which was the first plant genome to achieve full sequence analysis. The Arabidopsis genome is about 12.5 million base pairs and contains about 26,000 genes encoding about 25,000 proteins.

A large number of mutants occurring at different loci have been obtained by physical (e.g., radiation treatment), chemical (e.g., EMS mutagenesis), and biological (e.g., translocation of DNA fragments into the Arabidopsis genome using plant endogenous transposons or Agrobacterium tumefaciens) methods. Several germplasm resource centers have been established to facilitate the acquisition and exchange of mutants. Today arabidopsis thaliana has become the most widely used model plant in the world, known as the “fruit fly of plants”.

Figure 3 Smiling Arabidopsis
Figure 3 Smiling Arabidopsis

After a long period of research, scientists have made great progress in understanding the development process of Arabidopsis, and its application value is gradually recognized. Here are two examples.

Increasing grain yield and improving the tolerance of grain crops to drought and other weather disasters are important issues in plant research. China is short of water resources, and the spatial and temporal distribution of water resources is extremely uneven. Extreme weather events have increased in recent years, posing a great threat to food production. Therefore, it is of great significance to improve the drought-resistant ability of crops to ensure the sustainable development of agricultural economy and food security in China.

Based on the functional gene research of Arabidopsis, scientists overexpressed Arabidopsis HARDY (HRD) gene in rice, and finally realized the improvement of water use efficiency and drought resistance of rice [1]. In Arabidopsis thaliana, the functional acquisition mutant HRD-D showed dark green leaves, developed root system, and increased expression of several abiotic stress-related genes. The ability to resist drought and high salt environment was significantly enhanced, and the expression of HRD gene in the mutant was increased. The overexpression of HRD in rice can increase the biomass of rice leaves and the number of vascular bundle sheath cells, improve photosynthetic efficiency and reduce transpiration, thus enhancing water use efficiency and drought resistance.

Auxin is a kind of low molecular weight plant hormone, which plays an important role in regulating various aspects of plant growth and development by regulating cell division, elongation and differentiation. In Arabidopsis, auxin functions through a ubiquitin-dependent protein degradation pathway and regulates downstream gene expression. Early in 1993, axR1, a branching mutant of Arabidopsis thaliana, was identified and found to be involved in a ubiquitin-dependent protein degradation pathway [2].

AXR1 can activate ubiquitin like protein RUB1 and promote the binding of RUB1 to CUL1 protein in SCFTIR1 complex. The mutation of AXR1 protein reduces the binding of RUB1 to CUL1 and the function of SCF complex, thereby reducing the auxin response [3]. Subsequently, Nedd8, a homolog of RUB1, was identified in animals. Studies have shown that Nedd8 is also necessary for the function of SCF complex [4], and SCF dysfunction is closely related to a variety of human diseases, such as cancer and Alzheimer’s disease [5]. Therefore, the study of auxin signaling pathway in Arabidopsis thaliana provides important help for understanding the pathogenesis of some human diseases.

The selection and utilization of model plants are of great significance for genetic analysis, gene cloning and functional research. Arabidopsis thaliana has become the most dazzling star in the field of plant research in the past 40 years due to its small plant, abundant fruit, short life cycle, simple genome and simple genetic operation. More than 6,000 laboratories around the world are conducting intensive research on arabidopsis growth and development and its response to the environment. It has made important contributions to food production, crop resistance, environmental protection and other fields. Let us remember this grass and the magical model plant — Arabidopsis thaliana.

References:

1.Karaba A., Dixit S., Greco R., et al. (2007) Improvement of water use efficiency in rice by expression of HARDY, an Arabidopsis drought and salt tolerance gene. Proc Natl Acad Sci USA 104: 15270-5.

2.Leyser H.M., Lincoln C.A., Timpte C., et al. (1993) Arabidopsis auxin-resistance gene AXR1 encodes a protein related to ubiquitin-activating enzyme E1. Nature 364: 161-4.

3.Parry G. and Estelle M. (2006) Auxin receptors: a new role for F-box proteins. Curr Opin Cell Biol 18: 152-6.

4.Petroski M.D. and Deshaies R.J. (2005) Function and regulation of cullin-RING ubiquitin ligases. Nat Rev Mol Cell Biol 6: 9-20.

5.Jones A.M., Chory J., Dangl J.L., et al. (2008) The impact of Arabidopsis on human health: diversifying our portfolio. Cell 2008. 133: 939-43.