High‐quality evergreen azalea genome reveals tandem duplication‐facilitated low‐altitude adaptability and floral scent evolution

Abstract

Summary Azalea belongs to Rhododendron, which is one of the largest genera of flowering plants and is well known for the diversity and beauty in its more than 1000 woody species. Rhododendron contains two distinct groups: the most high‐altitude and a few low‐altitude species; however, the former group is difficult to be domesticated for urban landscaping, and their evolution and adaptation are little known. Rhododendron ovatum has broad adaptation in low‐altitude regions but possesses evergreen characteristics like high‐altitude species, and it has floral fragrance that is deficient in most cultivars. Here we report the chromosome‐level genome assembly of R. ovatum, which has a total length of 549 Mb with scaffold N50 of 41 Mb and contains 41 264 predicted genes. Genomic micro‐evolutionary analysis of R. ovatum in comparison with two high‐altitude Rhododendron species indicated that the expansion genes in R. ovatum were significantly enriched in defence responses, which may account for its adaptability in low altitudes. The R. ovatum genome contains much more terpene synthase genes (TPSs) compared with the species that lost floral fragrance. The subfamily b members of TPS are involved in the synthesis of sesquiterpenes as well as monoterpenes and play a major role in flora scent biosynthesis and defence responses. Tandem duplication is the primary force driving expansion of defence‐responsive genes for extensive adaptability to the low‐altitude environments. The R. ovatum genome provides insights into low‐altitude adaptation and gain or loss of floral fragrance for Rhododendron species, which are valuable for alpine plant domestication and floral scent breeding.

Chromosome‐level genome assembly and functional characterization of terpene synthases provide insights into the volatile terpenoid biosynthesis of Wurfbainia villosa

“…In the present study, the analyses of enzymes involved in terpenoid biosynthesis pathways suggest that the expansion of the TPS family, primarily through tandem gene duplications, may have led to the terpenoid diversity in W. villosa . It has been reported that the catalytic production of TPS is related to the sequence similarity (Karunanithi et al., 2020; Wang et al., 2021); in general, WvTPSs in the same tandem gene cluster tend to have closer evolutionary relationships and more similar catalytic products. For example, WvTPS35 and WvTPS37 from tandem gene cluster 10 were found to have similar catalytic products (Figure 5a; Figure S14).…”

De Novo Genome Assembly of Chinese Plateau Honeybee Unravels Intraspecies Genetic Diversity in the Eastern Honeybee, Apis cerana

“…Large-scale RNA interference experiments in C. elegans [ 81 , 82 ] and D. melanogaster [ 83 ] revealed that about 65% and 85% of the genes are dispensable in these two species, respectively; when the loss of a gene causes pathway dysfunction, the organism will choose alternative pathways to ensure the stable performance of the pathway function [ 84 ]. The most direct manifestation of “gene gain” events is the increase in the number of genes, which can help individuals adapt to the environment in which they survive [ 85 , 86 ].…”

Dissecting the subtropical adaptation traits and cuticle synthesis pathways via the genome of the subtropical blueberryVaccinium darrowii

“…We identified several genome characteristics that possibly contributed to the adaptation of V. darrowii to subtropical climates. Tandem duplicates contribute to gene family expansions and allow alternative transcriptional regulation, and thus have been considered a common strategy for adaptive evolution to altered environments 123,124 . A clear functional bias in the tandemly duplicated genes has been observed in plants, making tandem genes good index for environmental adaptation 123,125,126 .…”