Amazing stuff!
"Most grain crops die after completing one life cycle, meaning that new plants must be sown each year. However, some wild relatives of rice are perennial and can live through multiple yearly cycles.
Dai et al. identified a locus coding for a duplicated microRNA with expression that is regulated by DNA methylation status. Some alleles of this locus confer the ability to propagate rice vegetatively. By generating rice lines harboring this microRNA, as well as genes for other perennial traits, the authors developed rice that could grow for more than a year. Although alleles of additional loci will be needed to make fully fertile perennial rice plants, this work provides insights into perennial traits in rice and is a step forward in genetic engineering efforts."
From the abstract:
"Structured Abstract
INTRODUCTION
Plants exhibit a wide variety of life history strategies. Rice (Oryza sativa), one of the most widely grown staple crops worldwide, is cultivated as an annual species, whereas several of its wild relatives, such as Oryza rufipogon, display a perennial growth habit characterized by sustained vegetative growth and repeated reproduction. During domestication, this perennial growth habit was largely lost, representing an important shift in the life history strategy of rice. However, the genetic basis responsible for this transition remains poorly understood.
RATIONALE
To address this question, we investigated the traits associated with the perennial growth habit using 446 accessions of perennial wild rice. In O. rufipogon, one of the key traits linked to its perennial growth habit is a grasslike plant architecture, characterized by extensive tillering, floral reversion, and vegetative propagation—a phenotype largely absent in modern cultivated rice. To delineate the genetic basis underlying this trait, we used a set of single-segment substitution lines derived from both wild and cultivated rice and identified a gene locus that harbors tandem microRNA156 genes (MIR156BC). Through expression pattern analysis and epigenomic profiling, we investigated how dynamic changes in miR156 abundance promote a vegetative perennial growth habit in O. rufipogon. Finally, we explored whether we could reproduce the vegetative perennial growth habit of O. rufipogon in cultivated rice by introgressing this gene locus along with loci associated with prostrate growth.
RESULTS
We identified Endless Branches and Tillers 1 (EBT1) as a key gene locus controlling vegetative propagation and floral reversion in O. rufipogon W1943. The EBT1 locus harbors two tandem MIR156BC genes and has been positively selected for. Whereas wild-type cultivars senesce after seed setting, plants carrying the EBT1 allele from O. rufipogon W194 (EBT1W1943) exhibit vigorous tiller bud outgrowth and sustained vegetative growth after flowering. Mechanistically, unlike MIR156BC in modern annual cultivars, MIR156BC expression in O. rufipogon can be reset in developing tiller buds after flowering. This expression pattern is associated with increased chromatin accessibility and a reduction in the repressive epigenetic marker H3K27me3 at a regulatory region of EBT1. The combination of PROSTRATE GROWTH 1, TILLER INCLINED GROWTH 1, and EBT1W1943 enables annual cultivated rice to largely recapitulate the vegetative perennial growth habit of O. rufipogon.
CONCLUSION
We have identified MIR156BC as a key determinant of perenniality in rice. The distinctive epigenetic state at the MIR156BC locus in O. rufipogon facilitates its resetting after flowering, which subsequently leads to floral reversion and vegetative perennial growth. Our findings not only offer fresh insights into the genetic basis of perenniality in cereals but also pave the way for the development of sustainable perennial rice cultivars in the future."
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