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Summary: 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 β‐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 β‐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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Variation in seed size is common among plant species, populations, and individuals. On the Qinghai-Tibet Plateau, previous studies have mainly focused on interspecific variation in seed size, with little information available regarding intraspecific variation. The alpine steppe is among the most important vegetation types on the plateau, where it plays a vital role in preserving landscape heterogeneity and diversity. Stipa purpurea Griseb., endemic to the Qinghai-Tibet Plateau, is the predominant species of the alpine steppe. In the present study, we measured seed characteristics of nine S. purpurea populations and analyzed possible sources and consequences of variation in these characteristics. Seed characteristics varied greatly among and within populations. Our findings suggest that variation in seed size and awn length may affect germination and dispersal, respectively. Surprisingly, environmental factors, rather than genome size, were significantly correlated with seed size. For example, relative humidity and number of windy days were strongly correlated with seed size and awn length, respectively. We believe that variation in seed characteristics is a consequence of complex environmental conditions correlated with longitude and latitude. The results indicated that variation in seed characteristics of S. purpurea is an adaptation to environmental conditions. Keywords: Stipa purpurea, seed characteristics, alpine steppe, genome size, Qinghai-Tibet Plateau. La variation de la taille des semences est frequente entre les especes vegetales, les populations et les individus. Sur le plateau du Qinghai-Tibet, les etudes precedentes se sont principalement concentrees sur la variation interspecifique de la taille des semences, d'oU le peu d'information en ce qui concerne la variation intraspecifique. La steppe alpine se trouve parmi les types de vegetation les plus importants du plateau, oU elle joue un role cle dans la preservation de l'heterogeneite et de la diversite du paysage. Stipapurpurea Griseb., endemique du plateau du Qinghai-Tibet, est l'espece qui predomine la steppe alpine. Dans la presente etude, les auteurs ont evalue les caracteristiques de neuf populations de S. purpurea et analyse les sources et les consequences possibles de la variation de ces caracteristiques. Les caracteristiques des semences variaient grandement entre et a l'interieur des populations. Leurs donnees suggerent que la variation dans la taille des semences et la longueur de la barbe peut affecter la germination et la dispersion, respectivement. Fait surprenant, les facteurs environnementaux, plutot que la taille du genome, etaient en correlation significative avec la taille de la semence. Par exemple, l'humidite relative et le nombre de jours venteux etaient fortement correles a la taille de la semence et la longueur de la barbe, respectivement. Les auteurs croient que la variation des caracteristiques des semences est une consequence des conditions environnementales complexes correlees a la longitude et la latitude. Les resultats ont indique que la variation des caracteristiques des semences de S. purpurea est une adaptation aux conditions environnementales. [Traduit par la Redaction] Mots-cles : Stipapurpurea, caracteristiques des semences, steppe alpine, taille du genome, plateau du Qinghai-Tibet., Introduction Plant seeds not only preserve and transmit genetic information--they are also an adaptation to ensure plants are able to establish in seasonally stressful environments (Fenner 1983). Seed size variation [...]