Genome-wide identification and expression analysis of the invertase gene family in common wheat

Background: The degradation of sucrose plays an important role in the process of crop biomass allocation and yield formation. Invertase (INV) irreversibly catalyzes the conversion of sucrose into glucose and fructose, which doomed its' important role in plant development and stress tolerance. However, the functions of INV genes in wheat, one of the most important crops, were less studied due to the polyploidy. Results: Here, we systematically analyzed the INV gene family based on the latest published wheat reference genomic information. A total of 126 TaINV genes were identified and classified into three classes based on the phylogenetic relationship and their gene structure. Of which, 11 and 83 gene pairs were identified as tandem and segmental duplication genes respectively, while the Ka/Ks ratios of tandem and segmental duplication TaINV genes were less than 1. Expression profile analysis shows that 18 TaINV genes have tissue-specific expression, and 54 TaINV genes were involved in stress response. Furthermore, RNA-seq showed that 35 genes are differentially expressed in grain weight NILs N0910-81L/N0910-81S, in which 9 TaINVs were stably detected by qRT-PCR at three time-points, 4, 7 and 10 DPA. Four of them (TaCWI47, TaCWI48, TaCWI50 and TaVI27) different expressed between the NILs resided in 4 QTL segments (QTGW.nwafu-5DL.1, QTGW.nwafu-5DL.2, QTGW.nwafu-7AS.1 and QTGW.nwafu-7AS.2). These findings facilitate function investigations of the wheat INV gene family and provide new insights into the grain development mechanism in wheat. Conclusions: Our results showed that allopolyploid events were the main reason for the expansion of the TaINV gene family in hexaploid wheat, and duplication genes might undergo purifying selection. The expression profiling of TaINV genes implied that they are likely to play an important role in wheat growth and development and adaption to stressful environments. And TaCWI47, TaCWI48, TaCWI50 and TaVI27 may have more important roles in grain developments. Our study lay a base for further dissecting the functional characterization of TaINV family members.

Molecular evidence for segmental duplication across chromosomes of soybean using transcription factor gene family

Duplication of genome is an important genetic innovation. Large genome size (1.1 Gb) along with ancient and recent duplication events make the soybean genome more complex. Analyzing the distribution and duplication event in soybean transcription family genes, the segmental duplication within chromosomes was revealed. Our study provides a strong evidence that the large segmental duplication event in genome architecture and evolution of soybean genome using simple method of sequence and order analysis of TF genes. Finally, a scheme for interrelationship of different chromosomes has been proposed.

NPGREAT: Assembly of the human subtelomere regions with the use of ultralong Nanopore reads and Linked-Reads

Background Human subtelomeric DNA regulates the length and stability of adjacent telomeres that are critical for cellular function, and contains many gene/pseudogene families. Large evolutionarily recent segmental duplications and associated structural variation in human subtelomeres has made complete sequencing and assembly of these regions difficult to impossible for many loci, complicating or precluding a wide range of genetic analyses to investigate their function. Results We present a hybrid assembly method, NanoPore Guided REgional Assembly Tool (NPGREAT), which combines Linked-Read data with ultralong nanopore reads spanning subtelomeric segmental duplications to potentially overcome these difficulties. Linked-Read sets identified by matches with 1-copy subtelomere sequence adjacent to segmental duplications are assembled and extended into the segmental duplication regions using Regional Extension of Assemblies using Linked-Reads (REXTAL). Telomere-containing ultralong nanopore reads are then used to provide contiguity and correct orientation for matching REXTAL sequence contigs as well as identification/correction of any misassemblies (associated primarily with tandem repeats). While we focus on subtelomeres, the method is generally applicable to assembly of segmental duplications and other complex genome regions. Our method was tested for a subset of representative subtelomeres with ultralong nanopore read coverage in GM12878. 10X Linked-Read datasets with high depth of coverage and a TELL-seq Linked-Read dataset with lower depth of coverage were each combined with the ultralong nanopore reads from the same genome to provide improved assemblies. Tandem repeat regions of the short-read assemblies, which are especially prone to misassembly due to collapse of matching tandemly repeated reads, were readily identified and properly sized by comparison with the nanopore reads. Conclusion The NPGREAT method resulted in extension of high-quality assemblies into otherwise inaccessible segmental duplication regions near telomeres, enhancing our ability to accurately assemble human subtelomere DNA. This information will enable improved analyses of the structure, function, and evolution of these key regions.

Genome-Wide Identification, Evolutionary And Expression Analyses of LEA Gene Family In Peanut (Arachis Hypogaea L.)

Background: Late embryogenesis abundant (LEA) proteins are a group of highly hydrophilic glycine-rich proteins, which accumulate in the late stage of seed maturation and are associated with many abiotic stresses. However, few peanut LEA genes had been reported, and the research on the number, location, structure, molecular phylogeny and expression of AhLEAs was very limited. Results: In this study, 126 LEA genes were identified in the peanut genome through genome-wide analysis and were further divided into eight groups. Sequence analysis showed that most of the AhLEAs (85.7 %) had no or only one intron. LEA genes were randomly distributed on 20 chromosomes. Compared with tandem duplication, segmental duplication played a more critical role in AhLEAs amplication, and 93 segmental duplication AhLEAs and 5 pairs of tandem duplication genes were identified. Synteny analysis showed that some AhLEAs genes come from a common ancestor, and genome rearrangement and translocation occurred among these genomes. Almost all promoters of LEAs contain ABRE, MYB recognition sites, MYC recognition sites, and ERE cis-acting elements, suggesting that the LEA genes were involved in stress response. Gene expression analyses revealed that most of the LEAs were expressed in the late stages of peanut embryonic development. LEA3 (AH16G06810.1, AH06G03960.1), and Dehydrin (AH07G18700.1, AH17G19710.1) were highly expressed in roots, stems, leaves and flowers. Moreover, 100 AhLEAs were involved in response to drought, low-temperature, or Al stresses. Some LEAs that were regulated by different abiotic stresses were also regulated by hormones including ABA, brassinolide, ethylene and salicylic acid. Interestingly, AhLEAs that were up-regulated by ethylene and salicylic acid showed obvious subfamily preferences.Conclusions: AhLEAs are involved in abiotic stress response, and segmental duplication plays an important role in the evolution and amplification of AhLEAs. The genome-wide identification, classification, evolutionary and expression analyses of the AhLEA gene family provide a foundation for further exploring the LEA genes’ function in response to abiotic stress in peanuts.

Identification, systematic evolution and expression analyses of the AAAP gene family in Capsicum annuum

Background The amino acid/auxin permease (AAAP) family represents a class of proteins that transport amino acids across cell membranes. Members of this family are widely distributed in different organisms and participate in processes such as growth and development and the stress response in plants. However, a systematic comprehensive analysis of AAAP genes of the pepper (Capsicum annuum) genome has not been reported. Results In this study, we performed systematic bioinformatics analyses to identify AAAP family genes in the C. annuum ‘Zunla-1’ genome to determine gene number, distribution, structure, duplications and expression patterns in different tissues and stress. A total of 53 CaAAAP genes were identified in the ‘Zunla-1’ pepper genome and could be divided into eight subgroups. Significant differences in gene structure and protein conserved domains were observed among the subgroups. In addition to CaGAT1, CaATL4, and CaVAAT1, the remaining CaAAAP genes were unevenly distributed on 11 of 12 chromosomes. In total, 33.96% (18/53) of the CaAAAP genes were a result of duplication events, including three pairs of genes due to segmental duplication and 12 tandem duplication events. Analyses of evolutionary patterns showed that segmental duplication of AAAPs in pepper occurred before tandem duplication. The expression profiling of the CaAAAP by transcriptomic data analysis showed distinct expression patterns in various tissues and response to different stress treatment, which further suggest that the function of CaAAAP genes has been differentiated. Conclusions This study of CaAAAP genes provides a theoretical basis for exploring the roles of AAAP family members in C. annuum.

Genome-wide identification and evolutionary analysis of RLKs involved in the response to aluminium stress in peanut

Background As an important cash crop, the yield of peanut is influenced by soil acidification and pathogen infection. Receptor-like protein kinases play important roles in plant growth, development and stress responses. However, little is known about the number, location, structure, molecular phylogeny, and expression of RLKs in peanut, and no comprehensive analysis of RLKs in the Al stress response in peanuts have been reported. Results A total of 1311 AhRLKs were identified from the peanut genome. The AhLRR-RLKs and AhLecRLKs were further divided into 24 and 35 subfamilies, respectively. The AhRLKs were randomly distributed across all 20 chromosomes in the peanut. Among these AhRLKs, 9.53% and 61.78% originated from tandem duplications and segmental duplications, respectively. The ka/ks ratios of 96.97% (96/99) of tandem duplication gene pairs and 98.78% (646/654) of segmental duplication gene pairs were less than 1. Among the tested tandem duplication clusters, there were 28 gene conversion events. Moreover, all total of 90 Al-responsive AhRLKs were identified by mining transcriptome data, and they were divided into 7 groups. Most of the Al-responsive AhRLKs that clustered together had similar motifs and evolutionarily conserved structures. The gene expression patterns of these genes in different tissues were further analysed, and tissue-specifically expressed genes, including 14 root-specific Al-responsive AhRLKs were found. In addition, all 90 Al-responsive AhRLKs which were distributed unevenly in the subfamilies of AhRLKs, showed different expression patterns between the two peanut varieties (Al-sensitive and Al-tolerant) under Al stress. Conclusions In this study, we analysed the RLK gene family in the peanut genome. Segmental duplication events were the main driving force for AhRLK evolution, and most AhRLKs subject to purifying selection. A total of 90 genes were identified as Al-responsive AhRLKs, and the classification, conserved motifs, structures, tissue expression patterns and predicted functions of Al-responsive AhRLKs were further analysed and discussed, revealing their putative roles. This study provides a better understanding of the structures and functions of AhRLKs and Al-responsive AhRLKs.

Genome-wide identification and expression analysis of the GhIQD gene family in upland cotton (Gossypium hirsutum L.)

Background Calmodulin (CaM) is one of the most important Ca2+ signaling receptors because it regulates diverse physiological and biochemical reactions in plants. CaM functions by interacting with CaM-binding proteins (CaMBPs) to modulate Ca2+ signaling. IQ domain (IQD) proteins are plant-specific CaMBPs that bind to CaM by their specific CaM binding sites. Results In this study, we identified 102 GhIQD genes in the Gossypium hirsutum L. genome. The GhIQD gene family was classified into four clusters (I, II, III, and IV), and we then mapped the GhIQD genes to the G. hirsutum L. chromosomes. Moreover, we found that 100 of the 102 GhIQD genes resulted from segmental duplication events, indicating that segmental duplication is the main force driving GhIQD gene expansion. Gene expression pattern analysis showed that a total of 89 GhIQD genes expressed in the elongation stage and second cell wall biosynthesis stage of the fiber cells, suggesting that GhIQD genes may contribute to fiber cell development in cotton. In addition, we found that 20 selected GhIQD genes were highly expressed in various tissues. Exogenous application of MeJA significantly enhanced the expression levels of GhIQD genes. Conclusions Our study shows that GhIQD genes are involved in fiber cell development in cotton and are also widely induced by MeJA. Thw results provide bases to systematically characterize the evolution and biological functions of GhIQD genes, as well as clues to breed better cotton varieties in the future.