The dynamic behaviour of seeds in soil seed banks depends on their ability to act as sophisticated environmental sensors to adjust their sensitivity thresholds for germination by dormancy mechanisms. Here we show that prolonged incubation of sugar beet fruits at low temperature (chilling at 5°C, generally known to release seed dormancy of many species) can induce secondary nondeep physiological dormancy of an apparently nondormant crop species. The physiological and biophysical mechanisms underpinning this cold-induced secondary dormancy include the chilling-induced accumulation of abscisic acid in the seeds, a reduction in the embryo growth potential and a block in weakening of the endosperm covering the embryonic root. Transcriptome analysis revealed distinct gene expression patterns in the different temperature regimes and upon secondary dormancy induction and maintenance. The chilling caused reduced expression of cell wall remodelling protein genes required for embryo cell elongation growth and endosperm weakening, as well as increased expression of seed maturation genes, such as for late embryogenesis abundant proteins. A model integrating the hormonal signalling and master regulator expression with the temperature-control of seed dormancy and maturation programmes is proposed. The revealed mechanisms of the cold-induced secondary dormancy are important for climate-smart agriculture and food security.

• Klíčová slova
• coat dormancy, cold-induced dormancy, embryo growth potential, endosperm weakening, germination temperature, secondary dormancy, seed transcriptomes, sugar beet,
• MeSH
• Beta vulgaris * genetika   MeSH
• klíčení fyziologie   MeSH
• kyselina abscisová metabolismus   MeSH
• semena rostlinná fyziologie   MeSH
• vegetační klid genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyselina abscisová MeSH

This article comments on: Nicola Schmidt, Kathrin M. Seibt, Beatrice Weber, Trude Schwarzacher, Thomas Schmidt, and Tony Heitkam, Broken, silent, and in hiding: tamed endogenous pararetroviruses escape elimination from the genome of sugar beet (Beta vulgaris), Annals of Botany Volume 128, Issue 3, 26 August 2021, Pages 281–291, https://doi.org/10.1093/aob/mcab042

• Klíčová slova
• Beta vulgaris, chromosome, endogenous viruses, epigenetics,
• MeSH
• Beta vulgaris * genetika   MeSH
• cukry MeSH
• genom rostlinný MeSH
• genomika MeSH
• Publikační typ
• komentáře MeSH
• práce podpořená grantem MeSH
• úvodníky MeSH
• Názvy látek
• cukry MeSH

There are 11 different varieties of Beta vulgaris L. that are used in the food industry, including sugar beets, beetroots, Swiss chard, and fodder beets. The typical red coloration of their tissues is caused by the indole-derived glycosides known as betalains that were analyzed in hypocotyl extracts by UV/Vis spectrophotometry to determine the content of betacyanins (betanin) and of betaxanthins (vulgaxanthin I) as constituents of the total betalain content. Fields of beet crops use to be also infested by wild beets, hybrids related to B. vulgaris subsp. maritima or B. macrocarpa Guss., which significantly decrease the quality and quantity of sugar beet yield; additionally, these plants produce betalains at an early stage. All tested B. vulgaris varieties could be distinguished from weed beets according to betacyanins, betaxanthins or total betalain content. The highest values of betacyanins were found in beetroots 'Monorubra' (9.69 mg/100 mL) and 'Libero' (8.42 mg/100 mL). Other beet varieties contained less betacyanins: Sugar beet 'Labonita' 0.11 mg/100 mL; Swiss chard 'Lucullus,' 0.09 mg/100 mL; fodder beet 'Monro' 0.15 mg/100 mL. In contrast with weed beets and beetroots, these varieties have a ratio of betacyanins to betaxanthins under 1.0, but the betaxanthin content was higher in beetcrops than in wild beet and can be used as an alternative to non-red varieties. Stability tests of selected varieties showed that storage at 22 °C for 6 h, or at 7 °C for 24 h, did not significantly reduce the betalain content in the samples.

• Klíčová slova
• beetcrops, beetroot, betalains, spectrophotometry, storage, weedbeet,
• MeSH
• Beta vulgaris chemie   genetika   MeSH
• betakyaniny analýza   chemie   MeSH
• betalainy analýza   MeSH
• betaxanthiny analýza   MeSH
• genotyp MeSH
• hypokotyl chemie   MeSH
• plevel chemie   MeSH
• rostlinné extrakty chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• betakyaniny MeSH
• betalainy MeSH
• betanin MeSH Prohlížeč
• betaxanthiny MeSH
• rostlinné extrakty MeSH

BACKGROUND: Sugar beet (Beta vulgaris) is an important crop of temperate climate zones, which provides nearly 30 % of the world's annual sugar needs. From the total genome size of 758 Mb, only 567 Mb were incorporated in the recently published genome sequence, due to the fact that regions with high repetitive DNA contents (e.g. satellite DNAs) are only partially included. Therefore, to fill these gaps and to gain information about the repeat composition of centromeres and heterochromatic regions, we performed chromatin immunoprecipitation followed by sequencing (ChIP-Seq) using antibodies against the centromere-specific histone H3 variant of sugar beet (CenH3) and the heterochromatic mark of dimethylated lysine 9 of histone H3 (H3K9me2). RESULTS: ChIP-Seq analysis revealed that active centromeres containing CenH3 consist of the satellite pBV and the Ty3-gypsy retrotransposon Beetle7, while heterochromatin marked by H3K9me2 exhibits heterogeneity in repeat composition. H3K9me2 was mainly associated with the satellite family pEV, the Ty1-copia retrotransposon family Cotzilla and the DNA transposon superfamily of the En/Spm type. In members of the section Beta within the genus Beta, immunostaining using the CenH3 antibody was successful, indicating that orthologous CenH3 proteins are present in closely related species within this section. CONCLUSIONS: The identification of repetitive genome portions by ChIP-Seq experiments complemented the sugar beet reference sequence by providing insights into the repeat composition of poorly characterized CenH3-chromatin and H3K9me2-heterochromatin. Therefore, our work provides the basis for future research and application concerning the sugar beet centromere and repeat-rich heterochromatic regions characterized by the presence of H3K9me2.

• Klíčová slova
• Beta vulgaris, CenH3, Centromere, ChIP-Seq, H3K9me2, Heterochromatin, Repeats,
• MeSH
• Beta vulgaris genetika   metabolismus   MeSH
• centromera metabolismus   MeSH
• chromatin genetika   metabolismus   MeSH
• chromatinová imunoprecipitace MeSH
• heterochromatin genetika   metabolismus   MeSH
• histony metabolismus   MeSH
• lysin metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• sekvenční analýza DNA MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• heterochromatin MeSH
• histony MeSH
• lysin MeSH
• rostlinné proteiny MeSH