Alfalfa(Medicago sativa L.)is one of the most important and widely cultivated forage crops.It is commonly used as a vegetable and medicinal herb because of its excellent nutritional quality and significant economic va...Alfalfa(Medicago sativa L.)is one of the most important and widely cultivated forage crops.It is commonly used as a vegetable and medicinal herb because of its excellent nutritional quality and significant economic value.Based on Illumina,Nanopore and Hi-C data,we assembled a chromosome-scale assembly of Medicago sativa spp.caerulea(voucher PI464715),the direct diploid progenitor of autotetraploid alfalfa.The assembled genome comprises 793.2 Mb of genomic sequence and 47,202 annotated protein-coding genes.The contig N50 length is 3.86 Mb.This genome is almost twofold larger and contains more annotated protein-coding genes than that of its close relative,Medicago truncatula(420 Mb and 44,623 genes).The more expanded gene families compared with those in M.truncatula and the expansion of repetitive elements rather than whole-genome duplication(i.e.,the two species share the ancestral Papilionoideae whole-genome duplication event)may have contributed to the large genome size of M.sativa spp.caerulea.Comparative and evolutionary analyses revealed that M.sativa spp.caerulea diverged from M.truncatula~5.2 million years ago,and the chromosomal fissions and fusions detected between the two genomes occurred during the divergence of the two species.In addition,we identified 489 resistance(R)genes and 82 and 85 candidate genes involved in the lignin and cellulose biosynthesis pathways,respectively.The near-complete and accurate diploid alfalfa reference genome obtained herein serves as an important complement to the recently assembled autotetraploid alfalfa genome and will provide valuable genomic resources for investigating the genomic architecture of autotetraploid alfalfa as well as for improving breeding strategies in alfalfa.展开更多
To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau （QTP） responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the ge...To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau （QTP） responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the genetic distribution pattern of 101 individuals of Potentilla glabra, comprising both the interior QTP and the plateau edge. Phylogenetic and network analyses of 31 recovered haplotypes identified three tentative clades （A, B and C）. Analysis of molecular variance （AMOVA） revealed that most of the genetic variability was found within populations （0.693）, while differentiations between populations were obviously distinct （Fst -- 0.307）. Two independent range expansions within clades A and B occurring at approximately 316 and 201 thousand years ago （kya） were recovered from the hierarchical mismatch analysis, and these two expansions were also confirmed by Fu＇s Fs values and ＇g＇ tests. However, distant distributions of clade C and private haplotypes from clades A and B suggest that they had survived the Last Glacial Maximum （LGM） and previous glaciers in situ since their origins. Our findings based on available limited samples support that multiple refugia of a few cold-enduring species had been maintained in the QTP platform during LGM and/or previous glacial stages.展开更多
Delayed selfing could provide ovules with an opportunity to be fertilized as a means of ＂pollination assurance＂ before the flowers wilt. It could, thus, be regarded as an adaptation to unpredictable pollinator envir...Delayed selfing could provide ovules with an opportunity to be fertilized as a means of ＂pollination assurance＂ before the flowers wilt. It could, thus, be regarded as an adaptation to unpredictable pollinator environments. Within the alpine biennial Gentianopsis paludosa, the showy flowers and herkogamy at the early stage of a flower＇s life cycle may favor outcrossing. As the flower ages, anthers contact the central stigma due to the elongation of all filaments, resulting in autonomous selfing. Flower visitors are extremely rare in a high altitude population; and examination of the mating system indicates that G. paludosa is self-pollinated under natural conditions in this population. While at the lower altitude, the bumblebee visitation rate is relatively high but possibly unreliable. Stigma receptivity is the highest on the third day of anthesis, and decreases thereafter. Pollen viability is the highest when flowers open, and gradually decreases later. Self-pollination of G. paludosa occurs at the late stage of a flower＇s lifecycle when stigma receptivity and pollen viability have both decreased, suggesting delayed selfing and assurance of seed production. This delayed selfing could assure seed production under the constraints of pollinator scarcity, but ensure outcrossing when pollinators were available. Such a flexible pollination mechanism is highly adaptive in the alpine environment of the Qinghai-Tibetan Plateau.展开更多
基金supported equally by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0502)the National Natural Science Foundation of China(31971391)further supported by the National Natural Science Foundation of China(41901056 and 31722055).
文摘Alfalfa(Medicago sativa L.)is one of the most important and widely cultivated forage crops.It is commonly used as a vegetable and medicinal herb because of its excellent nutritional quality and significant economic value.Based on Illumina,Nanopore and Hi-C data,we assembled a chromosome-scale assembly of Medicago sativa spp.caerulea(voucher PI464715),the direct diploid progenitor of autotetraploid alfalfa.The assembled genome comprises 793.2 Mb of genomic sequence and 47,202 annotated protein-coding genes.The contig N50 length is 3.86 Mb.This genome is almost twofold larger and contains more annotated protein-coding genes than that of its close relative,Medicago truncatula(420 Mb and 44,623 genes).The more expanded gene families compared with those in M.truncatula and the expansion of repetitive elements rather than whole-genome duplication(i.e.,the two species share the ancestral Papilionoideae whole-genome duplication event)may have contributed to the large genome size of M.sativa spp.caerulea.Comparative and evolutionary analyses revealed that M.sativa spp.caerulea diverged from M.truncatula~5.2 million years ago,and the chromosomal fissions and fusions detected between the two genomes occurred during the divergence of the two species.In addition,we identified 489 resistance(R)genes and 82 and 85 candidate genes involved in the lignin and cellulose biosynthesis pathways,respectively.The near-complete and accurate diploid alfalfa reference genome obtained herein serves as an important complement to the recently assembled autotetraploid alfalfa genome and will provide valuable genomic resources for investigating the genomic architecture of autotetraploid alfalfa as well as for improving breeding strategies in alfalfa.
基金Supported by the Frontier Project of the Knowledge Innovation Program of Northwest Plateau Institute of Biology of the Chinese Academy of Sciences,National Natural Science Foundation of China (30725004)the Programfor New Century Excellent Talents,Ministry of Education of China (NCET-05-0886)a Grant-in Aid for Scientific Research (A) from the Ministry of Education,Culture,Sports,Science and Technology,Government of Japan(18255004)
文摘To date, little is still known about how alpine species occurring in the Qinghai-Tibetan Plateau （QTP） responded to past climatic oscillations. Here, by using variations of the chloroplast trnT-L, we examined the genetic distribution pattern of 101 individuals of Potentilla glabra, comprising both the interior QTP and the plateau edge. Phylogenetic and network analyses of 31 recovered haplotypes identified three tentative clades （A, B and C）. Analysis of molecular variance （AMOVA） revealed that most of the genetic variability was found within populations （0.693）, while differentiations between populations were obviously distinct （Fst -- 0.307）. Two independent range expansions within clades A and B occurring at approximately 316 and 201 thousand years ago （kya） were recovered from the hierarchical mismatch analysis, and these two expansions were also confirmed by Fu＇s Fs values and ＇g＇ tests. However, distant distributions of clade C and private haplotypes from clades A and B suggest that they had survived the Last Glacial Maximum （LGM） and previous glaciers in situ since their origins. Our findings based on available limited samples support that multiple refugia of a few cold-enduring species had been maintained in the QTP platform during LGM and/or previous glacial stages.
基金support by the Chinese Academy of Sciences (Key Innovation Plan KSCX-SW2-106 and the Special Fund for Outstanding PhD Dissertations to Jian-Quan Liu)the National Natural Science Foundation of China (30270253and 30700096)
文摘Delayed selfing could provide ovules with an opportunity to be fertilized as a means of ＂pollination assurance＂ before the flowers wilt. It could, thus, be regarded as an adaptation to unpredictable pollinator environments. Within the alpine biennial Gentianopsis paludosa, the showy flowers and herkogamy at the early stage of a flower＇s life cycle may favor outcrossing. As the flower ages, anthers contact the central stigma due to the elongation of all filaments, resulting in autonomous selfing. Flower visitors are extremely rare in a high altitude population; and examination of the mating system indicates that G. paludosa is self-pollinated under natural conditions in this population. While at the lower altitude, the bumblebee visitation rate is relatively high but possibly unreliable. Stigma receptivity is the highest on the third day of anthesis, and decreases thereafter. Pollen viability is the highest when flowers open, and gradually decreases later. Self-pollination of G. paludosa occurs at the late stage of a flower＇s lifecycle when stigma receptivity and pollen viability have both decreased, suggesting delayed selfing and assurance of seed production. This delayed selfing could assure seed production under the constraints of pollinator scarcity, but ensure outcrossing when pollinators were available. Such a flexible pollination mechanism is highly adaptive in the alpine environment of the Qinghai-Tibetan Plateau.
