According to incomplete statistics, closed pollination was found in 703 species in 234 genera in 51 families of angiosperms, of which facultative closed pollination accounted for the largest proportion, accounting for about 77.3% of the total. Closed pollination facilitates the formation of inbred and inbred lines and can prevent genetic drift. Previous studies on the genomic level of facultative closed pollinators have not been reported. Cleistogenes songorica is a typical facultative pollinator of the grass family, with spikelets in the leaf sheath for complete closed pollination (CL), while the apex flowering vessel is flowering pollination (CH). Unlike other type II plants, the type II florets of Cryptophyllum phylloscopus are gradually formed in the leaf sheath during the same growth period with the onset of jointing, until the top spike is withdrawn to produce CH florets, while the type II florets of most facultative pollinators are induced by light time, adversity, etc. Cryptophyllum ambulatory grass is a perennial superhympedic C4 plant, which is a group and dominant species in arid desert grasslands. Therefore, the deciphering of the genome sequence of Cryptospercus tanabe can accelerate the analysis of the pollination and drought tolerance mechanism of closed flowers and the application of closed flowers in production.
Professor Yanrong Wang's team from the College of Grassland Agricultural Science and Technology of Lanzhou University used the domesticated and selected "Tengger" mandarinless cryptophyllus as the material, and used PacBio CLR (40Kb) to sequence the data to obtain 172 Gb (316x). Assemble to obtain a genome of 540.12Mb, contig N50 up to 21.28Mb. Combined with Hi-C data, 20 chromosomes were attached to the genome, and the mounting rate was as high as 97.85%. The BUSCO assessment result reached 98.25%. It was verified that the telomeres of 20 chromosomes were assembled, of which 10 were gap-free. Prediction annotations yielded 54,383 genes.
Cryptophyllum amanita is heterologous tetraploid ( 2n = 4x = 40 ) , but no ancestral species have been found. Through collinear and single-copy gene analysis, the researchers successfully distinguished the two subgenomes of AB without mangosteensis, and through comparative genomic analysis, it was found that the tetraploidy event occurred before about 19.2Mya, and four of the chromosomes were rearranged. Evolutionary analysis showed that Oropetium thomaeum and Eragrostis tef belonged to the same subfamily Chloridoideae, but compared with thrush, the cryptophyllus was more closely related to the resurrection grass, and it was determined that the cryptophyllum anonosa did not belong to the thrush family.
Fig. 1 Phenotypic and subgroup differentiation of Cryptophyllum non-mangosteensis
The researchers constructed a network of flower development regulation and identified genes from various families at the genome-wide level. Comparative analysis found that 10 families of the photoperiod pathway expanded. ABCDE model genes that regulate flower organ development are expressed differentially in the flower organs of CH and CL florets. Morphological observations have found that CL pulp tablets are almost not developing. Studies have shown that some members of the AP2 family regulate the development of endophyllum, anthers and pulp tablets, of which miR172 targets AP2 family member Cly1 to inhibit its expression, pulp flakes develop, and florets open. Nine homologous genes of Cly1 were identified in Cryptospermum ambulatory, among which there were bi-base variants different from Cly1 at the targets of CsAP2_8, CsAP2_9 and miR172-l. The function of the two was verified in rice. Studies have demonstrated that the interaction of CsAP2_9 and miR172-l plays an important role in regulating closed pollination.
Fig. 2 Identification and verification of flowering genes at the whole genome level of cryptophyllum nonchalant
The reference genome and drought adaptation evolutionary analysis of Cryptoscephalus anchovy reported in this study, as well as the identification and analysis of pollinator genes of closed flowers, have important guiding significance for the cultivation of drought-tolerant new castils. The domesticated and selected "Tengger" cryptocephalus of Lanzhou University has been promoted and applied in degraded grasslands and mine ecological restoration in arid desert areas.
Recently, the research work was titled "The genome of Cleistogenes songoricaprovides a blueprint for functional dissection of dimorphic flower differentiation and drought adaptability" in Plant Biotechnology Published online in the Journal. Lanzhou University is the first unit to complete the thesis. Professor Zhang Jiyu of the College of Grassland Agricultural Science and Technology of Lanzhou University is the first author of the paper, and his team of doctoral students Wu Fan and Yan Qi are the co-first authors of the paper. Professor Wang Yanrong of Lanzhou University and Academician German Spangenberg of the Victorian Institute of Agricultural Biology of La Trobe University in Australia are the co-corresponding authors of the paper. The research has been funded by the National Key Basic Research and Development Program (973 Program), the National Natural Science Foundation of China, and the Gansu Provincial Science and Technology Major Project.
Original link: https://onlinelibrary.wiley.com/doi/10.1111/pbi.13483
Editor: Li Zhaoqiu
Editor-in-charge: Xu Wenyan