Comparative Analysis of Banyan Trees and Wasp Genomes Revealed Basis of Aerial Root Formation and Coevolution of Plant-Pollinators
Genomics of Aerial Root Formation and Coevolution of Plant-Pollinators. Zhang et al., Cell, 2020; https://doi.org/10.1016/j.cell.2020.09.043
In biology, the coevolution of plants and pollinators is one of the most remarkable examples of distant species adaption and speciation. Banyan tree (Ficus sp.) is one of the ancient genomes (~ 75 million years old) of plant kingdom. The special characters of Ficus genus such as hemi-epiphytic nature, enclosed inflorescence, fig-wasp obligate mutualism and sex determination are important in understanding many evolutionary phenomena. The exciting association among Ficus plants and their obligate pollinator wasp species serves as a model system for studying evolution, and diversification of plant and pollinators.
The authors' Zhang et al. (2020) sequenced the genomes of two Ficus species, Ficus microcarpa (monoecy & hemi-epiphytic) and Ficus hispida (functional dioecy & territorial) and pollinator wasp of F. microcarpa, Eupristina verticillata. The study shows an enhanced accumulation of auxins promotes aerial root development in F. microcarpa. Subsequently, through comparative genome analyses, authors show duplication of biosynthesis (TAR and YUC encoding), signalling (CUL1, SINAT5) and transport (PIN1) of auxin genes and light receptor encoding genes (CRY2 and PHR2) in F. microcarpa is the basis of light-dependent aerial root formation and development. The re-sequencing and comparative analysis of 60 F1 individuals identify a male-specific FhAG2 as a candidate gene for sex determination in F. hispida. Further, authors reveal the divergence time scale (∼41.5 my) of pollinator wasps E. verticillata and Ceratosolen solmsi is close to the estimate for the divergence of respective host trees F. microcarpa and F. hispida (∼40 mya). Population genomic analyses show coadaptation and codiversification of genomic signatures for fruit size and production of specific volatile organic compounds in fig species of subgenus Sycomorus, and organ size and chemosensory receptors in obligate pollinator wasp species. The work gives an important update and evolutionary genomics perspective on plant-pollinator coevolution. The data and findings of the investigations are of broader interest to plant evolutionary biologists and geneticists.