On November 7, 2024, Science published a research paper titled "A trade-off between investment in molecular defense repertoires and growth in plants", which revealed that wild plants sacrifice growth when increasing defense gene density to enhance resistance, while agricultural plants have changed this growth-defense trade-off due to long-term artificial selection. It is worth mentioning that this paper has only two authors.
This study is based on the growth-defense trade-off hypothesis, that is, plants must make a trade-off between defense and growth in resource allocation. When plants face pathogen threats, investing more resources in defense may sacrifice growth rate and reproductive capacity. Therefore, this study proposed and verified whether the trade-off pattern between defense investment and growth in wild plants and agricultural plants is different.
The defense mechanism of plants mainly relies on nucleotide-binding leucine-rich repeat (NLR) receptors, which can recognize specific pathogens and activate effector-triggered immunity (ETI). To further explore the relationship between defense investment and growth, the research team analyzed a wide range of plant data, including specific leaf area (SLA) and NLR gene density, to compare the differences in defense strategies between wild and agricultural plants.
The study analyzed genomic data and trait data from 187 plants, including 122 wild plants and 65 agricultural plants. These data came from multiple databases, including NCBI's genome database and plant trait databases such as AusTraits and BIEN.
To ensure data integrity, the authors removed low-quality genomic data and divided plants into wild and agricultural groups, and calculated and compared their NLR gene density, SLA and other characteristics.
Pearson correlation analysis and structural equation modeling (SEM) were used to control interspecific phylogenetic differences to analyze the relationship between defense gene density (including NLR, repeat and single copy density) and SLA.
The study found that in wild plants, higher NLR gene density significantly reduced the SLA value of plants, that is, increasing the density of defense genes would slow the growth rate of plants. This suggests that wild plants sacrifice growth by improving defense mechanisms when facing pathogen pressure.
In contrast, there was no significant correlation between NLR gene density and growth (SLA) in agricultural plants. The study speculates that agricultural plants have been disturbed by long-term artificial selection on the association between growth and resistance genes, making the trade-off pattern between defense and growth different from that of wild plants.
The analysis also showed that the repeat density of NLR genes was positively correlated with their overall density, indicating that gene duplication may be a key mechanism for NLR intragenomic amplification. The presence of duplicate genes may play an important role in the evolution of NLR genes and the maintenance of defense functions.
Figure 1. The piecewiseSEM analysis testing effects between NLR, repeat, and singleton gene density, habitat area, and growth. (Giolai, et al., 2024)
This study verified the growth-defense trade-off hypothesis from a cross-species perspective and revealed significant differences in defense mechanisms between wild plants and agricultural plants.
In natural environments, plants face a variety of survival pressures and increase NLR gene density to enhance immunity, but this also sacrifices growth efficiency accordingly.
Agricultural plants show different defense investment patterns from wild plants due to the long-term influence of human selection pressure, which may be because agricultural plants focus on yield during the selection process and reduce the diversity of NLR genes.
This study used large-scale, cross-species plant genome and functional data to reveal differences in growth and defense strategies among different plant species, providing new insights into ecology and evolutionary biology.
This study further demonstrated how human selection affects the genome structure of plants and their ecological adaptability, providing inspiration for agricultural breeding and plant resistance research.
The results of this study not only expand the understanding of the trade-off between plant growth and defense, but also provide a theoretical basis for future applications in plant resistance breeding and ecology.
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