The chromosome-level genome assembly of Cananga odorata provides insights into its evolution and terpenoid biosynthesis.

Cananga odorata is known as a natural perfume tree of the Annonaceae family in Magnoliales. However, its phylogenetic position and the molecular mechanisms involved in the biosynthesis of the floral volatile organic compounds (VOCs) remain unclear. Here, by combining a variety of sequencing platforms, we present a telomere-to-telomere (T2T) genome of C. odorata with 735.83 Mb, which represents the highest integrity and assembly quality of genome in magnoliid plants reported to date. Phylogenetic analysis based on multiple datasets and approaches showed that C. odorata, as a member of magnoliids, is sister to eudicots, after their divergence from monocots. Metabolomic of VOCs in the essential oil and flowers scent showed that sesquiterpenes, especially ß-caryophyllene, were the major compounds. Two CoTPS21 homologues derived from tandem duplication events were highly expressed during flower development and were identified as the key sesquiterpene synthases for the production of ß-caryophyllene. In addition, CoSPL3 and CoSPL9 were considered as potential transcription factors for activating the expression of CoTPS21 homologues. Our results shed light on the molecular mechanisms underlying the biosynthesis of the unique floral fragrance in C. odorata and provide new insights into the phylogenetic position of magnoliids.

ICE1 interacts with IDD14 to transcriptionally activate QQS to increase pollen germination and viability.

In flowering plants, sexual reproductive success depends on the production of viable pollen grains. However, the mechanisms by which QUA QUINE STARCH (QQS) regulates pollen development and how transcriptional activators facilitate the transcription of QQS in this process remain poorly understood. Here, we demonstrate that INDUCER OF CBF EXPRESSION 1 (ICE1), a basic helix-loop-helix (bHLH) transcription factor, acts as a key transcriptional activator and positively regulates QQS expression to increase pollen germination and viability in Arabidopsis thaliana by interacting with INDETERMINATE DOMAIN14 (IDD14). In our genetic and biochemical experiments, overexpression of ICE1 greatly promoted both the activation of QQS and high pollen viability mediated by QQS. IDD14 additively enhanced ICE1 function by promoting the binding of ICE1 to the QQS promoter. In addition, mutation of ICE1 significantly repressed QQS expression; the impaired function of QQS and the abnormal anther dehiscence jointly affected pollen development of the ice1-2 mutant. Our results also showed that the enhancement of pollen activity by ICE1 depends on QQS. Furthermore, QQS interacted with CUT1, the key enzyme for long-chain lipid biosynthesis. This interaction both promoted CUT1 activity and regulated pollen lipid metabolism, ultimately determining pollen hydration and fertility. Our results not only provide new insights into the key function of QQS in promoting pollen development by regulating pollen lipid metabolism, but also elucidate the mechanism that facilitates the transcription of QQS in this vital developmental process.

Functional Differentiation of the Duplicated Gene BrrCIPK9 in Turnip (Brassica rapa var. rapa).

Gene duplication is a key biological process in the evolutionary history of plants and an important driving force for the diversification of genomic and genetic systems. Interactions between the calcium sensor calcineurin B-like protein (CBL) and its target, CBL-interacting protein kinase (CIPK), play important roles in the plant's response to various environmental stresses. As a food crop with important economic and research value, turnip (Brassica rapa var. rapa) has been well adapted to the environment of the Tibetan Plateau and become a traditional crop in the region. The BrrCIPK9 gene in turnip has not been characterized. In this study, two duplicated genes, BrrCIPK9.1 and BrrCIPK9.2, were screened from the turnip genome. Based on the phylogenetic analysis, BrrCIPK9.1 and BrrCIPK9.2 were found located in different sub-branches on the phylogenetic tree. Real-time fluorescence quantitative PCR analyses revealed their differential expression levels between the leaves and roots and in response to various stress treatments. The differences in their interactions with BrrCBLs were also revealed by yeast two-hybrid analyses. The results indicate that BrrCIPK9.1 and BrrCIPK9.2 have undergone Asparagine-alanine-phenylalanine (NAF) site divergence during turnip evolution, which has resulted in functional differences between them. Furthermore, BrrCIPK9.1 responded to high-pH (pH 8.5) stress, while BrrCIPK9.2 retained its ancestral function (low K+), thus providing further evidence of their functional divergence. These functional divergence genes facilitate turnip's good adaptation to the extreme environment of the Tibetan Plateau. In summary, the results of this study reveal the characteristics of the duplicated BrrCIPK9 genes and provide a basis for further functional studies of BrrCBLs-BrrCIPKs in turnip.

Morphological and structural characteristics of the elytra reduce impact damage to ladybird beetles.

Beetle elytra act as natural protective covers and effectively shield their flexible abdomens and fragile hindwings from damage. The existing studies have attributed this contribution of the elytra to its honeycomb structures. In this combined experimental and theoretical study, we used the seven-spotted ladybird beetle to demonstrate that both biological morphology and the hollow structure of the dome-like elytra combined to reduce damage during falling. The falling ladybird beetles had a high probability (59.52%) of hitting the ground with the costal edge of the elytra. This strategy could assist with converting the translational energy into rotational kinetic energy, resulting in the reduction of the impulse during falling. In addition, the hollow structures on the elytra could further absorb the residual impact energy. In the future, this biological paradigm could be used as a basis for the development of falling/landing techniques for advanced robots.

Chromosome-level genome assembly of Hippophae gyantsensis.

Hippophae gyantsensis, which is a native tree species in China, is ideal for windbreak and sand-fixing forests. It is an economically and ecologically valuable tree species distributed exclusively in the Qinghai-Tibet Plateau in China. In our study, we assembled a chromosome-level genome of H. gyantsensis using Illumina sequencing, Nanopore sequencing and chromosome structure capture technique. The genome was 716.32 Mb in size with scaffold N50 length of 64.84 Mb. A total of 716.25 Mb genome data was anchored and orientated onto 12 chromosomes with a mounting rate of up to 99.99%. Additionally, the genome was found to comprise approximately 56.84% repeat sequences, of which long terminal repeats(LTRs) that accounted for 33.19% of the entire genome. Meanwhile, a total of 32,316 protein-coding genes were predicted, and 91.07% of these genes were functionally annotated. We also completed a series of comparative genomic analyses to provide researchers with useful reference material for future studies on seabuckthorn.

A telomere-to-telomere gap-free reference genome assembly of avocado provides useful resources for identifying genes related to fatty acid biosynthesis and disease resistance.

Avocado (Persea americana Mill.) is an economically valuable plant because of the high fatty acid content and unique flavor of its fruits. Its fatty acid content, especially the relatively high unsaturated fatty acid content, provides significant health benefits. We herein present a telomere-to-telomere gapless genome assembly (841.6 Mb) of West Indian avocado. The genome contains 40 629 predicted protein-coding genes. Repeat sequences account for 57.9% of the genome. Notably, all telomeres, centromeres, and a nucleolar organizing region are included in this genome. Fragments from these three regions were observed via fluorescence in situ hybridization. We identified 376 potential disease resistance-related nucleotide-binding leucine-rich repeat genes. These genes, which are typically clustered on chromosomes, may be derived from gene duplication events. Five NLR genes (Pa11g0262, Pa02g4855, Pa07g3139, Pa07g0383, and Pa02g3196) were highly expressed in leaves, stems, and fruits, indicating they may be involved in avocado disease responses in multiple tissues. We also identified 128 genes associated with fatty acid biosynthesis and analyzed their expression patterns in leaves, stems, and fruits. Pa02g0113, which encodes one of 11 stearoyl-acyl carrier protein desaturases mediating C18 unsaturated fatty acid synthesis, was more highly expressed in the leaves than in the stems and fruits. These findings provide valuable insights that enhance our understanding of fatty acid biosynthesis in avocado.

Chromosome-level genome assembly of Hippophae rhamnoides variety.

Fructus hippophae (Hippophae rhamnoides spp. mongolica×Hippophae rhamnoides sinensis), a hybrid variety of sea buckthorn that Hippophae rhamnoides spp. mongolica serves as the female parent and Hippophae rhamnoides sinensis serves as the male parent, is a traditional plant with great potentials of economic and medical values. Herein, we gained a chromosome-level genome of Fructus hippophae about 918.59 Mb, with the scaffolds N50 reaching 83.65 Mb. Then, we anchored 440 contigs with 97.17% of the total genome sequences onto 12 pseudochromosomes. Next, de-novo, homology and transcriptome assembly strategies were adopted for gene structure prediction. This predicted 36475 protein-coding genes, of which 36226 genes could be functionally annotated. Simultaneously, various strategies were used for quality assessment, both the complete BUSCO value (98.80%) and the mapping rate indicated the high assembly quality. Repetitive elements, which occupied 63.68% of the genome, and 1483600 bp of non-coding RNA were annotated. Here, we provide genomic information on female plants of a popular variety, which can provide data for pan-genomic construction of sea buckthorn and for the resolution of the mechanism of sex differentiation.