Abrupt drought-flood alternation (T1) is a meteorological disaster that frequently occurs during summer in southern China and the Yangtze river basin, often causing a significant loss of rice production. In this study, the response mechanism of yield decline under abrupt drought-flood alternation stress at the panicle differentiation stage was analyzed by looking at the metabolome, proteome as well as yield and physiological and biochemical indexes. The results showed that drought and flood stress caused a decrease in the yield of rice at the panicle differentiation stage, and abrupt drought-flood alternation stress created a synergistic effect for the reduction of yield. The main reason for the decrease of yield per plant under abrupt drought-flood alternation was the decrease of seed setting rate. Compared with CK0 (no drought and no flood), the net photosynthetic rate and soluble sugar content of T1 decreased significantly and its hydrogen peroxidase, superoxide dismutase, peroxidase activity increased significantly. The identified differential metabolites and differentially expressed proteins indicated that photosynthesis metabolism, energy metabolism pathway and reactive oxygen species response have changed strongly under abrupt drought-flood alteration stress, which are factors that leads to the rice grain yield reduction.
Monilinia fructicola is a plant pathogenic fungus usually causing brown rot in the stone fruit crops. Here, the complete mitochondrial genome of M. fructicola is first reported, and the length of the circular genome was 163,790 bp and the content of GC was 31%. Meanwhile, it contained 28 transfer RNA (tRNA) genes, 30 protein-coding genes (PCGs) with many intron sequences and 2 ribosomal RNA (rRNA) genes. Phylogenetic analysis with 15 Leotiomycetes species indicated that M. fructicola was clustered in the Sclerotiniaceae family and was closely narrowed to Botryotinia fuckeliana and Sclerotinia scleroticrum. In addition, the valuable gene information of the mitochondrial genome was provided, and the study on the control of this destructive pathogen would be facilitated.
In this study, the complete mitochondrial genome of O. gracilis was sequenced and assembled before being compared with related species. As the second largest mitogenome reported in the family Ophiocordycipitaceae, the mitogenome of O. gracilis (voucher OG201301) is a circular DNA molecule of 134,288 bp that contains numerous introns and longer intergenomic regions. UCA was detected as anticodon in tRNA-Sec of O. gracilis, while comparative mitogenome analysis of nine Ophiocordycipitaceae fungi indicated that the order and contents of PCGs and rRNA genes were considerably conserved and could descend from a common ancestor in Ophiocordycipitaceae. In addition, the expansion of mitochondrial organization, introns, gene length, and order of O. gracilis were determined to be similar to those of O. sinensis, which indicated common mechanisms underlying adaptive evolution in O. gracilis and O. sinensis. Based on the mitochondrial gene dataset (15 PCGs and 2 RNA genes), a close genetic relationship between O. gracilis and O. sinensis was revealed through phylogenetic analysis. This study is the first to investigate the molecular evolution, phylogenetic pattern, and genetic structure characteristics of mitogenome in O. gracilis. Based on the obtained results, the mitogenome of O. gracilis can increase understanding of the genetic diversity and evolution of cordycipitoid fungi.
Soluble starch synthase IIa gene (SSIIa) is one of the key genes involved in the synthesis of amylopectin and a major gene controlling the gelatinization temperature of rice. In this study, specific molecular markers are designed for the four functional SNPs of the SSIIa gene, namely 264 (SNP1), 1810 (SNP2), 2209 (SNP3), and 2340–2341 (SNP4). In addition, 91 rice varieties are tested and the correlation of these SNPs with the structure of amylopectin, RVA profile characteristics, and gelatinization temperature are also analyzed. The results show that SNP1 (C/G) and SNP2 (A/G) of the SSIIa gene are significantly associated with the A:B value, SBV, and gelatinization temperature. The SNP4 (GC/TT) is significantly associated with the gelatinization temperature. Among the four haplotypes, namely C‐A‐A‐GC (HP1), C‐A‐G‐TT (HP2), G‐G‐G‐GC (HP3), and C‐A‐G‐GC (HP4), HP1 varieties show shorter chain length (CL) and exterior chain length (ECL), HP3 show a lower A:B value, whereas HP3 and HP4 varieties show lower PKV, BDV, and higher CPV, SBV, gelatinization temperature. The results suggest that different nonsynonymous SNPs in SSIIa may alter the activity of the SSIIa enzyme and further affect the CL and ECL of amylopectin, resulting in a different RVA profile and gelatinization temperature of starch.
Xylaria hypoxylo
n is a noticeable black fungus, and also habitual to cluster on rotting wood. In this study, the high-quality whole-genome of
X. hypoxylon
strain SFY20170806 was sequenced on the Illumina sequencing platform. The complete mitochondrial genome of
X. hypoxylon
was assembled and annotated. The single circular structure of 129,366 bp length is the largest species found in the order Xylariales. The overall GC content is 29.7% and gene composition includes 13 protein-coding genes (PCGs), 30 transfer RNA genes(tRNA), 2 ribosomal RNA genes(rRNA) and 6 open reading frames (ORF). Phylogenetic tree was constructed to validate the evolutionary relationship based on the complete mitogenomes from twelve taxa of four species of Xylariales, four species of Hypocreales, two species of Helotiales, one species of Microascales and
X. hypoxylon
. Phylogenetic analysis demonstrated that
X. hypoxylon
has a special evolutionary status and close genetic relationship with
Annulohypoxylon stygium
.
Seed aging is the key factor leading to the loss of genetic integrity. In this study, the seeds of Dongxiang wild rice, Xianggu, 9194 and Nipponbare were kept in a plant incubator with constant temperature and humidity for artificial aging treatment. The genetic integrity of germplasm resources with different germination gradients were analyzed using 44 SSR markers. The results suggested that different accessions could be ranked in order of aging resistance from highest to lowest as common wild rice > Xianggu > 9194 > Nipponbare. In order to maintain the genetic diversity of rice, the population size for reproduction and regeneration should be between 60 and 140. After aging, the number of polymorphic alleles, the number of specific single plant, the ratio of polymorphic bands, the number of alleles, the number of effective alleles, gene diversity index and Shannon index of different accessions all decreased with the decrease of germination rate. The germination rate of 60% was the critical value to maintain genetic integrity. Besides, the genetic integrity of eighteen SSR markers was rapidly lost or significantly increased. The regions of these markers were closely related to seed viability or genetic integrity. This study provides a theoretical basis for determining the population size for reproduction and regeneration and the critical value of germination rate of rice resources.
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