An annual plant completes its entire life cycle within one year, including fertilization, seed germination, flowering, fruiting, and death. However, multi fruiting perennial plants will not die after flowering and fruiting, and will continue to produce leaves. They will continue to bloom and bear fruit in the following year, and so on in a cyclical manner. Compared to higher animals, perennial higher plants have an incredible lifespan limit. They are so old that they cannot even annotate their annual rings, and only the carbon-14 method can calculate their longevity geometry. However, they are still "young" and bloom with new green in every spring.

It is generally believed that perennial plants are more ancient, while annual plants evolved from their perennial ancestors. However, the genome of perennial plants has tens of thousands of genes and billions of base pairs, and finding the key genes that determine longevity is like searching for a needle in a haystack. Until now, no perennial gene has been cloned worldwide, and the related evolutionary path is still unclear.

It is generally believed that perennial crops have the characteristic of sowing and harvesting multiple times at once, which can save labor and machinery costs, improve soil structure, and help maintain food security and ecological security. Therefore, cultivating and promoting perennial crops has positive production and application value, and is a key area of global agricultural green development that has received much attention.

On May 28, Wang Jiawei's research team from the Center for Excellence and Innovation in Molecular Plant Science, Chinese Academy of Sciences, and the Key Laboratory of Plant Efficient Carbon Sink, published a research paper entitled "Academic conversion between annual and polycarpic perennial flooring behavior in the Brassicaceae" online on Cell. The research strategy of this work is to use plant genera and species with rich life history (annual, biennial, and perennial) strategy variations as models, and to locate key genes that determine the evolution of perennial and plant life history strategies through the construction of cross species genetic populations and positive genetic methods.

The cruciferous plants include various important vegetables and oil crops, and the model plant Arabidopsis also belongs to this family. Wang Jiawei's team conducted research on the Flora of China and collected plants from all over the world. They selected a pair of hybrid annual/perennial plant combinations from the Brassicaceae family, including the Brassicaceae genus and the Brassicaceae genus. Among them, Himalayan mustard and Nevada sugar mustard are perennial plants with multiple fruiting plants; Xiaohua Sugar Mustard is a once fruiting annual plant; However, the egg leaf mustard exhibits facultative winter annual/multiple fruiting perennial characteristics. On this basis, the study constructed two genetic mapping populations with separated life history phenotypes and used high-throughput sequencing technology to determine the genotype of each individual plant. The study identified three gene intervals in both the genus Arabidopsis and the genus Arabidopsis, suggesting that the life cycle strategy evolution of cruciferous plants exhibits cross species conservation. Research has found that in the gene functional annotation of the control model plant Arabidopsis, there is a class of closely related MADS box transcription factor coding genes in these three genetic intervals, namely FLOWERING LOCUS C (FLC), FLOWERING LOCUS M (FLM), and MADSAFECTINGFLOWERING (MAF), which have the function of inhibiting plant flowering and reproductive growth.

In order to verify the impact of the three genes mentioned above on perennial and life history strategies, researchers used CRISPR/Cas9 genome editing technology to specifically knock out the FLC gene, FLM gene, and MAF gene in perennial Himalayan mustard. Through hybridization, the mutated genes were combined in different ways, reproducing the trajectory of the plant's gradual evolution from multiple fruity perennial to biennial and then to annual. When all FLC, FLM, and MAF genes remained functional, the plant exhibited a robust multi fruity perennial phenotype; Missing one or two genes can lead to facultative life cycle strategies in plants (weak perennial/biennial/winter annual); When all three genes are completely missing, the plant transforms into a single fruiting annual.

The RNA seq and H3K27me3 ChIP seq experiments of parental and F1 generation plants showed that the FLC like MADS box genes of annual small flower sugar mustard were more likely to be stably suppressed after vernalization, while genes from perennial Nevada sugar mustard tended to be reset after vernalization. This difference is the core molecular basis for the multiple establishment of the life habits of sturdy perennial plants, and is determined by the specific sequence of the genes themselves. Research has found that although FLC, FLM, and MAF are closely related, they are not the same in terms of gene function and expression levels, as well as reset time and intensity.
Based on the above experimental results, the team proposes that the evolution of life history strategies in cruciferous plants, namely the transition between perennial/biennial/annual, is a continuous process determined by the dose superposition effect of three FLC class MADS box genes. The diversity of expression patterns, protein functions, and epigenetic reset patterns of FLC genes, FLM genes, and MAF genes, as well as their different permutations and combinations, enable plants to have diverse life history strategies to adapt to changing growth environments.

This study transformed the annual model plant Arabidopsis from a single fruiting annual to a multi fruiting perennial by introducing a perennial FLC gene. This suggests that annual plants such as Arabidopsis have a prerequisite for becoming multi fruiting perennial plants, and that perennial FLC like MADS box genes may be a necessary and sufficient condition for establishing the perennial living habits of cruciferous plants.

The above achievements have achieved the free conversion of perennial and annual Brassicaceae plants for the first time internationally, laying a theoretical foundation for the precise design and targeted cultivation of perennial rapeseed crop varieties that can adapt to specific climatic and geographical environments in the future. In addition, due to the developed root systems of perennial crops, they can ensure high water and fertilizer utilization, reduce soil erosion, and fix carbon in the soil layer. Therefore, designing perennial cruciferous plants will be beneficial for the sustainable development of agriculture in China and the achievement of the "dual carbon" goal.

The research work was supported by the National Natural Science Foundation of China Basic Science Center Program and the Chinese Academy of Sciences Strategic Pilot Science and Technology Project (Category B).

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