Transcriptome analysis provides insights into lignin synthesis and MAPK signaling pathway that strengthen the resistance of bitter gourd (Momordica charantia) to Fusarium wilt.

Fusarium wilt is a typical soil-borne disease caused by Fusarium oxysporum f. sp. momordicae (FOM) in bitter gourd. In this study, by comparing sequencing data at multiple time points and considering the difference between resistant (R) and susceptible (S) varieties, differentially expressed genes were screened out. Short time-series expression miner analysis revealed the upregulated expression trend of genes, which were enriched in phenylpropanoid biosynthesis, plant-pathogen interaction, and mitogen-activated protein kinase signaling pathway. Further, observation of the microstructure revealed that the R variety may form tyloses earlier than the S variety to prevent mycelium diffusion from the xylem vessel. After Fusarium wilt infection, the enzymatic activities of superoxide dismutase, peroxidase, phenylalanine ammonia lyase, and catalaseas well as levels of superoxide anion and malondialdehyde were increased in the R variety higher than those in the S variety. This study provides a reference to elucidate the disease resistance mechanism of bitter gourd.

Family-1 UDP glycosyltransferases in pear (Pyrus bretschneideri): Molecular identification, phylogenomic characterization and expression profiling during stone cell formation.

Stone cells are a characteristic trait of pear fruits, and excessive stone cell formation has a significant negative impact on the texture and flavour of the pulp. Lignin is one of the main components of stone cells. Family-1 uridine diphosphate-glycosyltransferases (UGTs) are responsible for the glycosylation modification of monolignols. However, information remains limited regarding the relationship between UGTs and stone cell formation. To address this problem, we identified 139 UGTs from the pear genome, which were distributed in 15 phylogenetic groups (A-M, O, and P). We also performed a collinearity analysis of UGTs among four Rosaceae plants (pear, peach, mei, and strawberry). Phylogenetic analysis suggested that 13 PbUGTs might be related to the glycosylation of monolignols. Analysis of expression patterns demonstrated that most putative monolignol glycosylation-related PbUGTs not only showed high expression levels in flowers and buds but were also induced by exogenous ABA, SA, and MeJA. In addition, the transcript level of Pbr005014.1 (named PbUGT72AJ2) was consistent with the changing trend of lignin content in pear fruit, and the transcript level was also higher in 'Dangshan Su' pear with higher lignin and stone cell contents. Subcellular localization results showed that PbUGT72AJ2 was located mainly in the cytomembrane and cytoplasm. Based on our study, PbUGT72AJ2 is considered to be a monolignol glycosylation-related UGT. Our results provide an important source for the identification of UGTs and a foundation for the future understanding and manipulation of lignin metabolism and stone cell formation in pear fruit.

Molecular identification, phylogenomic characterization and expression patterns analysis of the LIM (LIN-11, Isl1 and MEC-3 domains) gene family in pear (Pyrus bretschneideri) reveal its potential role in lignin metabolism.

Lignin is the main component of stone cells, which are a key factor in determining pear quality. Therefore, modification of lignin biosynthesis has important implications for regulating stone cell formation. LIMs are involved in plant development, stress response and metabolism. However, there is still a lack of knowledge about the pear LIM family and lignin-related LIMs. To address this problem, we identified 14 LIMs from the pear genome and named them. Phylogenomic and feature domain analysis showed that they were divided into CRP- and DA&DAR-LIM groups and five subclades. LIMs from the genomes of four rosids (Prunus mummer, Prunus persica, Fragaria vesca and Vitis vinifera) were also identified, and microsynteny analysis revealed the most orthologous gene pairs in the cross of pear/grape and pear/mei. The transcript levels of PbLIMs were significantly affected by SA, ABA and MeJA. Spatio-temporal expression analysis showed that PbLIMs of the δLIM2 subfamily were highly expressed in the flowers. Changes in the expression levels of PbWLIM1a and PbWLIM1b during fruit development was consistent with the changes in lignin content. Combining phylogenetic analyses, protein three-dimensional structure determination and sequence alignment analyses, these two genes were suggested as lignin-related PbLIMs. Subcellular localization results showed that PbWLIM1a and PbWLIM1b were located mainly in the chloroplast. This study lays the foundation for revealing the mechanism of LIM-mediated lignin metabolism to regulate stone cell formation.

In Silico Genome-Wide Analysis of Respiratory Burst Oxidase Homolog (RBOH) Family Genes in Five Fruit-Producing Trees, and Potential Functional Analysis on Lignification of Stone Cells in Chinese White Pear.

: The accumulation of lignin in fruit has a significant negative impact on the quality of fruit-producing trees, and in particular the lignin formation stimulates the development of stone cells in pear fruit. Reactive oxygen species (ROS) are essential for lignin polymerization. However, knowledge of the RBOH family, a key enzyme in ROS metabolism, remains unknown in most fruit trees. In this study, a total of 40 RBOHs were identified from five fruit-producing trees (Pyrusbretschneideri, Prunuspersica, Citrussinensis, Vitisvinifera, and Prunusmume), and 10 of these sequences came from Pyrusbretschneideri. Multiple sequence alignments revealed that all 10 PbRBOHs contained the NADPH_Ox domain and the six alpha-helical transmembrane domains (TM-I to TM-VI). Chromosome localization and interspecies phylogenetic tree analysis showed that 10 PbRBOHs irregularly distributed on 8 chromosomes and 3 PbRBOHs (PbRBOHA, PbRBOHB, and PbRBOHD) are closely related to known lignification-related RBOHs. Furthermore, hormone response pattern analysis showed that the transcription of PbRBOHs is regulated by SA, ABA and MeJA. Reverse transcription-quantitative real-time polymerase chain reaction (qRT-PCR) and transcriptome sequencing analysis showed that PbRBOHA, PbRBOHB, and PbRBOHD accumulated high transcript abundance in pear fruit, and the transcriptional trends of PbRBOHA and PbRBOHD was consistent with the change of stone cell content during fruit development. In addition, subcellular localization revealed that PbRBOHA and PbRBOHD are distributed on the plasma membrane. Combining the changes of apoplastic superoxide (O2.-) content and spatio-temporal expression analysis, these results indicate that PbRBOHA and PbRBOHD, which are candidate genes, may play an important role in ROS metabolism during the lignification of pear stone cells. This study not only provided insight into the molecular characteristics of the RBOH family in fruit-producing trees, but also lays the foundation for studying the role of ROS in plant lignification.

[Effects of organic matters and temperature on the anaerobic biodegradation of nonylphenol polyethoxylates].

The biodegradation of nonylphenol polyethoxylates (NPEOs) was studied under three different reductive conditions (methanogenesis, denitrification, and desulfuration conditions). Effects of organic matter and temperature on the biodegradation of NPEOs were also studied. The results showed that NP9EO could be rapidly biodegraded under three different reductive conditions. Gulcose and sodium acetate could inhibit NP9EO biodegradation while yeast extract could enhance the biodegradation. Temperature coefficients (u), which was relative with rate coefficient (k), under methanogenesis, denitrification, and desulfuration conditions were 19.93 kJ/mol, 23.13 kJ/mol, 27.00 kJ/mol respectively, when temperature ranged from 15 degrees C to 35 degrees C. The result suggested that the biodegradation rate constant of NP9EO under desulfuration condition was more sensitive to temperature than those of denitrification and methanogenesis treatments. These results could provide useful information on bioremendation of NPEOs contaminants.