Image: Traditional methods of plant regeneration require the use of plant growth regulators such as hormones, which can be species specific and labor intensive. In a new study, scientists have developed a new plant regeneration system by regulating the function and expression of genes involved in dedifferentiation (cell proliferation) and redifferentiation (organogenesis) of plant cells. View more
Traditional methods of plant regeneration require the use of plant growth regulators such as hormones, which can be species specific and labor intensive. In a new study, scientists have developed a new plant regeneration system by regulating the function and expression of genes involved in dedifferentiation (cell proliferation) and redifferentiation (organogenesis) of plant cells.
Plants have been the main source of food for animals and humans for many years. In addition, the plants are used to extract various pharmaceutical and therapeutic compounds. However, their misuse and growing demand for food highlight the need for new plant breeding methods. Advances in plant biotechnology could solve future food shortages by producing genetically modified (GM) plants that are more productive and resilient to climate change.
Naturally, plants can regenerate entirely new plants from a single “totipotent” cell (a cell that can give rise to multiple cell types) by dedifferentiating and redifferentiating into cells with different structures and functions. Artificial conditioning of such totipotent cells through plant tissue culture is widely used for plant protection, breeding, production of transgenic species and for scientific research purposes. Traditionally, tissue culture for plant regeneration requires the use of plant growth regulators (GGRs), such as auxins and cytokinins, to control cell differentiation. However, optimal hormonal conditions can vary significantly depending on the plant species, culture conditions and tissue type. Therefore, creating optimal exploration conditions can be a time-consuming and labor-intensive task.
To overcome this problem, Associate Professor Tomoko Ikawa, together with Associate Professor Mai F. Minamikawa from Chiba University, Professor Hitoshi Sakakibara from Nagoya University Graduate School of Bio-Agricultural Sciences and Mikiko Kojima, an expert technician from RIKEN CSRS, developed a universal method for plant control through regulation. Expression of “developmentally regulated” (DR) cell differentiation genes to achieve plant regeneration. Published in Volume 15 of Frontiers in Plant Science on April 3, 2024, Dr. Ikawa provided further information about their research work, stating: “Our system does not use external PGRs, but instead uses transcription factor genes to control cell differentiation. similar to pluripotent cells induced in mammals.”
The researchers ectopically expressed two DR genes, BABY BOOM (BBM) and WUSCHEL (WUS), from Arabidopsis thaliana (used as a model plant) and examined their effect on tissue culture differentiation of tobacco, lettuce and petunia. BBM encodes a transcription factor that regulates embryonic development, whereas WUS encodes a transcription factor that maintains stem cell identity in the region of the shoot apical meristem.
Their experiments showed that expression of Arabidopsis BBM or WUS alone is not sufficient to induce cell differentiation in tobacco leaf tissue. In contrast, coexpression of functionally enhanced BBM and functionally modified WUS induces an accelerated autonomous differentiation phenotype. Without the use of PCR, transgenic leaf cells differentiated into callus (disorganized cell mass), green organ-like structures and adventitious buds. Quantitative polymerase chain reaction (qPCR) analysis, a method used to quantify gene transcripts, showed that Arabidopsis BBM and WUS expression correlated with the formation of transgenic calli and shoots.
Considering the crucial role of phytohormones in cell division and differentiation, the researchers quantified the levels of six phytohormones, namely auxin, cytokinin, abscisic acid (ABA), gibberellin (GA), jasmonic acid (JA), salicylic acid (SA) and its metabolites in transgenic plant crops. Their results showed that the levels of active auxin, cytokinin, ABA, and inactive GA increase as cells differentiate into organs, highlighting their roles in plant cell differentiation and organogenesis.
In addition, the researchers used RNA sequencing transcriptomes, a method for qualitative and quantitative analysis of gene expression, to evaluate patterns of gene expression in transgenic cells exhibiting active differentiation. Their results showed that genes related to cell proliferation and auxin were enriched in differentially regulated genes. Further examination using qPCR revealed that the transgenic cells had increased or decreased expression of four genes, including genes that regulate plant cell differentiation, metabolism, organogenesis, and auxin response.
Overall, these results reveal a new and versatile approach to plant regeneration that does not require external application of PCR. In addition, the system used in this study may improve our understanding of the fundamental processes of plant cell differentiation and improve biotechnological selection of useful plant species.
Highlighting the potential applications of his work, Dr. Ikawa said, “The reported system could improve plant breeding by providing a tool for inducing cellular differentiation of transgenic plant cells without the need for PCR. Therefore, before transgenic plants are accepted as products, society will speed up plant breeding and reduce associated production costs.”
About Associate Professor Tomoko Igawa Dr. Tomoko Ikawa is an assistant professor at the Graduate School of Horticulture, Center for Molecular Plant Sciences, and Center for Space Agriculture and Horticulture Research, Chiba University, Japan. Her research interests include plant sexual reproduction and development and plant biotechnology. Her work focuses on understanding the molecular mechanisms of sexual reproduction and plant cell differentiation using various transgenic systems. She has several publications in these fields and is a member of the Japan Society of Plant Biotechnology, the Botanical Society of Japan, the Japanese Plant Breeding Society, the Japanese Society of Plant Physiologists, and the International Society for the Study of Plant Sexual Reproduction.
Autonomous differentiation of transgenic cells without external use of hormones: expression of endogenous genes and behavior of phytohormones
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Post time: Aug-22-2024