Mechanisms for early morphological establishment of plant primordium

Morphogenesis is one of
the central questions in developmental biology research.
The final morphology of plant organs is heavily influenced
by their early primordinal morphology.
Therefore, understanding the developmental mechanisms of primordium morphology is crucial
to understanding the morphological construction of plant organs.
However, while many factors that regulate primordium development have been identified over the years, the specific biological processes these factors influence and the mechanisms that ultimately determine the morphology of the primitive are still unclear
.

In response to this problem, on October 21, 2022, the Wang Ying Research Group of the Chinese Academy of Sciences, the Krzysztof Wabnik Research Group of the Polytechnic University of Madrid, Spain, and the State Key Laboratory of Protein and Plant Gene Research of Peking University and the Jiao Yuling Research Group of the School of Life Sciences published a report entitled "Differential growth dynamics control aerial organ" in Current Biology geometry" (DOI: 10.
1016/j.
cub.
2022.
09.
055), revealing how differences in cell growth patterns determine how leaf primordium and flower primordium develop from initially similar morphology to significantly different three-dimensional morphology
.

Figure 1: Pattern diagram where growth patterns determine the shape of the primorium

THIS STUDY FIRST TRACKED THE MORPHOLOGICAL CHANGES OF LEAF PRIMORDIUM AND FLOWER PRIMORDIUM DURING DEVELOPMENT AND THE EXPRESSION RANGE OF KEY GENES REVOLUTA (REV) AND KANADI1 (KAN1) IN THE NEAR AND FAR AXIAL REGION THROUGH IN VIVO IMAGING, AND FOUND THAT ALTHOUGH THE TWO PRIMORDIUMS HAD SIMILAR INITIAL STATES, THEY WOULD GRADUALLY PRODUCE MORPHOLOGICAL DIFFERENTIATION AND RELATIVE CHANGES IN REV-KAN1 expression zoning: the leaf primordium became a flat form symmetrical on both sides, and the expression range of REV and KAN1 was basically the same.
The flower primordium maintains a radially symmetrical morphology, and REV expression gradually occupies most of
the primordium.
This suggests that the near and far axial planes may have different relative growth rates
in different shapes of primitives.

Fig.
2: Morphological differentiation of leaf primordium (A-D) and flower primordium (E-H) and relative changes of REV-KAN1 expression zoning

In this study, the growth rate of the near and far axial planes in different primoriums was quantitatively analyzed by continuous time point imaging, and it was found that there were completely different growth patterns in the primorium: the lateral axial surface of the leaf primordium grew faster than the periaxial surface, while the opposite was true
in the flower primorium.
FURTHER ANALYSIS SHOWED THAT THE FAST-GROWING REGIONS IN THE LEAF PRIMORDIUM AND FLOWER PRIMORDIUM CORRESPONDED
TO THE EXPRESSION OF PRESSED FLOWER (PRS) AND LEAFY (LFY), RESPECTIVELY.
Based on the above experimental results, the researchers established a computer model
of the primordial morphology with the growth mode of the primordium as the main variable.
The simulation results show that adjusting the growth mode parameters can indeed affect the original base morphology, and the obtained primordium morphological changes can be confirmed
in the corresponding transgenic plants.
The study also compared the differences in auxin flow direction and cell wall chemical and mechanical properties in leaf primordium and flower primordium, and simulated the morphological development dynamics
of the primordium at a depth that was difficult to observe experimentally.
These experimental and simulation results, together with previous studies of the research group, established a high-resolution primordium growth model at the cellular level, and theoretically analyzed the necessary conditions
for the formation of leaf primordium and flower primordium morphology.
Computer models not only prove that growth patterns determine primordinal morphology, but also provide possible explanations
for the establishment of differential growth patterns.

Figure 3: Leaf primordium (A, C-E) and flower primordium (B, F-H) have different growth patterns

Figure 4: Leaf primordium (A-C) and flower primordium (H-N) have different auxin flow directions

This work adopts the idea of comparative research, combined with biological experiments and computer simulations, and uses interdisciplinary methods to explain the key mechanism of plant primordinal morphology, and also fills the cognitive gap
between gene expression and differential phenotype.

Peng Ziyuan, a master's student from the School of Life Sciences of the University of Science and Technology, Daniel Alique, a doctoral student at the Polytechnic University of Madrid, Spain, and Xiong Yuanyuan, a doctoral graduate from the Institute of Genetics of the Chinese Academy of Sciences, are the co-first authors of the paper.
Professor Jiao Yuling from the School of Life Sciences, Peking University, Krzysztof Wabnik Fellow at the Polytechnic University of Madrid, and Associate Professor Wang Ying from the University of Science and Technology of China are the co-corresponding authors
of this paper.
The research was supported
by the Wang Kuancheng Education Fund, the National Natural Science Foundation of China, and the Key R&D Program of the Ministry of Science and Technology.