How a Key Protein Pair Controls Growth and Hormone Production in Tomato Plants

Greg Howard
28th August, 2024

How a Key Protein Pair Controls Growth and Hormone Production in Tomato Plants

Image Source: Natural Science News, 2024

Key Findings

  • The study from the University of Idaho reveals that SINA1 and BSD1 regulate vegetative growth in tomato plants by controlling gibberellin (GA) biosynthesis
  • SINA1 tags BSD1 for destruction, reducing its levels, which in turn decreases the expression of the growth-promoting gene BRG1
  • Reduced GA levels in plants with high SINA1 or knocked-out BSD1 and BRG1 lead to dwarfism, but applying bioactive GA3 restores normal growth
In the realm of plant biology, understanding the mechanisms controlling vegetative growth is crucial for optimizing crop yields and improving agricultural productivity. The recent study from the University of Idaho[1] sheds light on the regulatory module involving the ubiquitin ligase seven in absentia1 (SINA1) and BSD1 (BTF2-like transcription factors, Drosophila synapse-associated proteins, and yeast DOS2-like proteins) in controlling vegetative growth in tomato plants. This research uncovers how these factors influence the production of gibberellin (GA), a key plant growth hormone. Vegetative growth in plants is a complex process regulated by a multitude of factors. Among these, the role of gibberellins (GAs) has been extensively studied. GAs are plant hormones that promote cell elongation, seed germination, and other growth processes. Prior studies have demonstrated that gibberellins, along with other hormones like brassinosteroids, play significant roles in plant development[2]. Moreover, the identification of quantitative trait loci (QTLs) related to plant height in crops like maize and sorghum has highlighted the importance of GAs in biomass yield[3]. The current study focuses on the interaction between SINA1 and BSD1 in regulating GA biosynthesis in tomato plants. SINA1 negatively regulates the protein level of BSD1 through a process called ubiquitin-proteasome-mediated degradation. Essentially, SINA1 tags BSD1 for destruction, reducing its levels in the plant. This degradation process is crucial because BSD1 plays a positive role in vegetative growth by activating the expression of BRG1, a gene that also promotes growth. In their experiments, the researchers created transgenic tomato plants that over-express SINA1 (SINA1-OX) and observed that these plants exhibited a dwarfism phenotype similar to that of BSD1-knockout (BSD1-KO) plants. This finding indicates that high levels of SINA1 suppress BSD1, leading to reduced growth. Additionally, when the BRG1 gene was knocked out (BRG1-KO), the plants also showed dwarfism, suggesting that BRG1 is another critical player in promoting vegetative growth. One of the key discoveries of this study is the identification of a novel binding site in the promoter region of BRG1, called the BSD1 binding site (BBS). BSD1 binds to this site to activate BRG1 expression, which in turn supports plant growth. This direct activation of BRG1 by BSD1 highlights a new layer of regulatory control in the GA biosynthesis pathway. The study further reveals that GA levels are reduced in the SINA1-OX, BSD1-KO, and BRG1-KO plants, all of which exhibit dwarfism. However, when bioactive GA3 (a form of gibberellin) was applied externally, the vegetative growth of these plants was restored. This finding underscores the pivotal role of GA in promoting plant growth and the importance of the SINA1-BSD1-BRG1 regulatory module in controlling GA biosynthesis. Moreover, BRG1 was found to be essential for the expression of multiple GA biosynthesis genes, and BSD1 directly activates three GA biosynthesis genes. This dual role of BSD1 in both direct and indirect regulation of GA production provides a comprehensive understanding of how vegetative growth is controlled at the molecular level. This study builds on previous research that identified the role of cytochrome P450 enzymes in the GA biosynthesis pathway[4]. Specifically, it expands our understanding of how different regulatory modules and transcription factors interact to control the levels of GAs in plants. By elucidating the SINA1-BSD1-BRG1 module, the researchers have provided valuable insights that could be applied to optimize plant architecture and improve crop productivity. In summary, the University of Idaho study reveals a complex regulatory module involving SINA1, BSD1, and BRG1 that controls vegetative growth in tomato plants through the regulation of GA biosynthesis. This research not only enhances our understanding of plant growth mechanisms but also offers potential strategies for improving crop yields by manipulating these regulatory pathways.

VegetablesBiochemPlant Science

References

Main Study

1) The SINA1-BSD1 Module Regulates Vegetative Growth Involving Gibberellin Biosynthesis in Tomato.

Published 27th August, 2024

https://doi.org/10.1002/advs.202400995

Related Studies

2) Brassinosteroid, gibberellin and phytochrome impinge on a common transcription module in Arabidopsis.

https://doi.org/10.1038/ncb2546

3) From dwarves to giants? Plant height manipulation for biomass yield.

https://doi.org/10.1016/j.tplants.2009.06.005

4) The CYP88A cytochrome P450, ent-kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway.

Journal: Proceedings of the National Academy of Sciences of the United States of America, Issue: Vol 98, Issue 4, Feb 2001


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