Genome-Wide Identification, Characterization, and Expression Analysis of Long-Chain Acyl-CoA Synthetases in Carya illinoinensis under Different Treatments.

As crucial enzymes in the lipid metabolic network, long-chain acyl-CoA synthases (LACSs) are members of the acyl-activated enzyme superfamily and play a crucial role in epidermal wax synthesis, plant lipid anabolic metabolism, and stress tolerance. In this study, 11 pecan LACS genes were identified and categorized into five groups and located on nine chromosomes. The significant degree of conservation in the AtLACS and CiLACS protein sequences was demonstrated by multiple sequence alignment and conserved motif analysis. Cis-acting element analysis identified numerous stress-responsive and hormone-inducible elements in the promoter regions of CiLACS genes. The expression levels of CiLACS9 and CiLACS9-1 were considerably up-regulated under salt and drought stress, according to the qRT-RCR study. Treatment with ABA also led to increased expression levels of CiLACS1, CiLACS1-1, CiLACS2, and CiLACS9-1. Notably, CiLACS4, CiLACS4-1, CiLACS9, and CiLACS9-1 exhibited peak expression levels at 135 days after anthesis and are likely to have been crucial in the accumulation of seed kernel oil. Moreover, the CiLACS9 gene was shown to be located in the cytoplasm. These findings offer a theoretical framework for clarifying the roles of LACS genes in the processes of pecan kernel oil synthesis and response to abiotic stressors.

Insight into the CBL and CIPK gene families in pecan (Carya illinoinensis): identification, evolution and expression patterns in drought response.

BACKGROUND: Calcium (Ca2+) serves as a ubiquitous second messenger and plays a pivotal role in signal transduction. Calcineurin B-like proteins (CBLs) are plant-specific Ca2+ sensors that interact with CBL-interacting protein kinases (CIPKs) to transmit Ca2+ signals. CBL-CIPK complexes have been reported to play pivotal roles in plant development and response to drought stress; however, limited information is available about the CBL and CIPK genes in pecan, an important nut crop. RESULTS: In the present study, a total of 9 CBL and 30 CIPK genes were identified from the pecan genome and divided into four and five clades based on phylogeny, respectively. Gene structure and distribution of conserved sequence motif analysis suggested that family members in the same clade commonly exhibited similar exon-intron structures and motif compositions. The segmental duplication events contributed largely to the expansion of pecan CBL and CIPK gene families, and Ka/Ks values revealed that all of them experienced strong negative selection. Phylogenetic analysis of CIPK proteins from 14 plant species revealed that CIPKs in the intron-poor clade originated in seed plants. Tissue-specific expression profiles of CiCBLs and CiCIPKs were analysed, presenting functional diversity. Expression profiles derived from RNA-Seq revealed distinct expression patterns of CiCBLs and CiCIPKs under drought treatment in pecan. Moreover, coexpression network analysis helped to elucidate the relationships between these genes and identify potential candidates for the regulation of drought response, which were verified by qRT-PCR analysis. CONCLUSIONS: The characterization and analysis of CBL and CIPK genes in pecan genome could provide a basis for further functional analysis of CiCBLs and CiCIPKs in the drought stress response of pecan.

Genome-Wide Identification and Expression Analysis of AMT and NRT Gene Family in Pecan (Carya illinoinensis) Seedlings Revealed a Preference for NH4+-N.

Nitrogen (N) is a major limiting factor for plant growth and crop production. The use of N fertilizer in forestry production is increasing each year, but the loss is substantial. Mastering the regulatory mechanisms of N uptake and transport is a key way to improve plant nitrogen use efficiency (NUE). However, this has rarely been studied in pecans. In this study, 10 AMT and 69 NRT gene family members were identified and systematically analyzed from the whole pecan genome using a bioinformatics approach, and the expression patterns of AMT and NRT genes and the uptake characteristics of NH4+ and NO3- in pecan were analyzed by aeroponic cultivation at varying NH4+/NO3- ratios (0/0, 0/100,25/75, 50/50, 75/25,100/0 as CK, T1, T2, T3, T4, and T5). The results showed that gene duplication was the main reason for the amplification of the AMT and NRT gene families in pecan, both of which experienced purifying selection. Based on qRT-PCR results, CiAMTs were primarily expressed in roots, and CiNRTs were majorly expressed in leaves, which were consistent with the distribution of pecan NH4+ and NO3- concentrations in the organs. The expression levels of CiAMTs and CiNRTs were mainly significantly upregulated under N deficiency and T4 treatment. Meanwhile, T4 treatment significantly increased the NH4+, NO3-, and NO2- concentrations as well as the Vmax and Km values of NH4+ and NO3- in pecans, and Vmax/Km indicated that pecan seedlings preferred to absorb NH4+. In summary, considering the single N source of T5, we suggested that the NH4+/NO3- ratio of 75:25 was more beneficial to improve the NUE of pecan, thus increasing pecan yield, which provides a theoretical basis for promoting the scale development of pecan and provides a basis for further identification of the functions of AMT and NRT genes in the N uptake and transport process of pecan.

Identification and Expression Analysis of MPK and MKK Gene Families in Pecan (Carya illinoinensis).

Mitogen-activated protein kinases consist of three kinase modules composed of MPKs, MKKs, and MPKKKs. As members of the protein kinase (PK) superfamily, they are involved in various processes, such as developmental programs, cell division, hormonal progression, and signaling responses to biotic and abiotic stresses. In this study, a total of 18 MPKs and 10 MKKs were annotated on the pecan genome, all of which could be classified into four subgroups, respectively. The gene structures and conserved sequences of family members in the same branch were relatively similar. All MPK proteins had a conserved motif TxY, and D(L/I/V)K and VGTxxYMSPER existed in all MKK proteins. Duplication events contributed largely to the expansion of the pecan MPK and MKK gene families. Phylogenetic analysis of protein sequences from six plants indicated that species evolution occurred in pecan. Organ-specific expression profiles of MPK and MKK showed functional diversity. Ka/Ks values indicated that all genes with duplicated events underwent strong negative selection. Seven CiPawMPK and four CiPawMKK genes with high expression levels were screened by transcriptomic data from different organs, and these candidates were validated by qRT-PCR analysis of hormone-treated and stressed samples.

Biochar Loaded with a Bacterial Strain N33 Facilitates Pecan Seedling Growth and Shapes Rhizosphere Microbial Community.

Biochar and beneficial microorganisms have been widely used in ecological agriculture. However, the impact of biochar loaded with microbes (BM) on plant growth remains to be understood. In this study, BM was produced by incubating pecan biochar with the bacterial strain N33, and the effects of BM on pecan growth and the microbial community in the rhizosphere were explored. BM application significantly enhanced the biomass and height of pecan plants. Meanwhile, BM treatment improved nutrient uptake in plants and significantly increased the chlorophyll, soluble sugars, and soluble proteins of plants. Furthermore, BM treatment improved the soil texture and environment. Finally, BM application substantially enhanced the diversity of soil fungi and bacteria as well as the relative abundances of the phyla Firmicutes and Chloroflexi, and families Bacillaceae and Paenibacillaceae, as shown by high-throughput sequencing. Together, this study clarified the growth-promotive effects of BM on pecan plants and suggested an alternative to synthetic fertilizers in their production.

Identification and Characterization of a Plant Endophytic Fungus Paraphaosphaeria sp. JRF11 and Its Growth-Promoting Effects.

Endophytic fungi establish mutualistic relationships with host plants and can promote the growth and development of plants. In this study, the endophytic fungus JRF11 was isolated from Carya illinoinensis. Sequence analysis of the internal transcribed spacer (ITS) region and 18S rRNA gene combined with colonial and conidial morphology identified JRF11 as a Paraphaosphaeria strain. Plant-fungus interaction assays revealed that JRF11 showed significant growth-promoting effects on plants. In particular, JRF11 significantly increased the root biomass and soluble sugar content of plants. Furthermore, transcriptome analysis demonstrated that JRF11 treatment reprogrammed a variety of genes involved in plant mitogen-activated protein kinase (MAPK) signaling and starch and sucrose metabolism pathways through Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. Our research indicates that beneficial endophytic fungi are able to interact with plants and exhibit outstanding plant growth-promoting activities.

Ammonium-nitrate mixtures dominated by NH4+-N promote the growth of pecan (Carya illinoinensis) through enhanced N uptake and assimilation.

Nitrogen (N) limits plant productivity, and its uptake and assimilation may be regulated by N sources, N assimilating enzymes, and N assimilation genes. Mastering the regulatory mechanisms of N uptake and assimilation is a key way to improve plant nitrogen use efficiency (NUE). However, it is poorly known how these factors interact to influence the growth process of pecans. In this study, the growth, nutrient uptake and N assimilation characteristics of pecan were analyzed by aeroponic cultivation at varying NH4 +/NO3 - ratios (0/0, 0/100,25/75, 50/50, 75/25,100/0 as CK, T1, T2, T3, T4, and T5). The results showed that T4 and T5 treatments optimally promoted the growth, nutrient uptake and N assimilating enzyme activities of pecan, which significantly increased aboveground biomass, average relative growth rate (RGR), root area, root activity, free amino acid (FAA) and total organic carbon (TOC) concentrations, nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate synthase (Fd-GOGAT and NADH-GOGAT), and glutamate dehydrogenase (GDH) activities. According to the qRT-PCR results, most of the N assimilation genes were expressed at higher levels in leaves and were mainly significantly up-regulated under T1 and T4 treatments. Correlation analysis showed that a correlation between N assimilating enzymes and N assimilating genes did not necessarily exist. The results of partial least squares path model (PLS-PM) analysis indicated that N assimilation genes could affect the growth of pecan by regulating N assimilation enzymes and nutrients. In summary, we suggested that the NH4 +/NO3 - ratio of 75:25 was more beneficial to improve the growth and NUE of pecan. Meanwhile, we believe that the determination of plant N assimilation capacity should be the result of a comprehensive analysis of N concentration, N assimilation enzymes and related genes.

A Stronger Rhizosphere Impact on the Fungal Communities Compared to the Bacterial Communities in Pecan Plantations.

Understanding microbial communities associated with bulk and rhizosphere soils will benefit the maintenance of forest health and productivity and the sustainable development of forest ecosystems. Based on MiSeq sequencing, we explored the differences between the bulk soil and the rhizosphere soil on bacterial and fungal communities of pecan plantation. Results suggested that rhizosphere-associated fungal rather than bacterial community structures differed from bulk soil, and rhizosphere soil had lower fungal diversity than bulk soil. Actinobacteria and Cantharellales were the bacterial and fungal biomarkers of the rhizosphere soil of pecan plantation, respectively. In addition, Pleosporales, which are mainly involved in saprophylaxis and plant pathogenic processes, was identified as one of the most important fungal biomarkers for the bulk soil, and the FunGuild predicted a higher relative abundance of pathogenic fungi in bulk soil compared to rhizosphere soil. The pH, ammonium nitrogen ( NH 4 + -N), nitrate nitrogen ( NO 3 - -N), and total carbon (TC) contents drove microbial community structure and composition. The bacterial network was simpler in the rhizosphere soil than in the bulk soil. However, fungi showed the opposite network pattern. Keystone species in bacterial and fungal networks were mostly involved in nutrient cycling and the C cycling, and were found to be enriched in the rhizosphere soil. Overall, in terms of bacterial and fungal communities, the rhizosphere soil behaves more healthily than the bulk soil and has a higher potential for nutrient cycling.

The complete chloroplast genome sequence of Carya illinoinensis cv. wichita and its phylogenetic analysis.

Carya illinoinensis is an important nut tree with high economic and ecological values. Here, we presented the complete chloroplast (cp) genome sequence of C. illinoinensis cv. wichita. The whole cp genome is 160,532 bp in length, displaying a typical quadripartite structure with a large single-copy (LSC) of 897,99 bp, a small single-copy (SSC) region of 18,751 bp, and a pair of inverted repeats (IRs) of 25,991 bp. A total of 128 genes were predicted to contain in the whole cp genome, including 83 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. The GC contents of the cp genome is 36.19%. Phylogenomic analysis suggested Carya illinoinensis as a sister species of C. cathayensis, C. kweichowensis, and Annamocarya sinensis.

Transcriptomic Analysis Provides Insights into Grafting Union Development in Pecan (Carya illinoinensis).

Pecan (Carya illinoinensis), as a popular nut tree, has been widely planted in China in recent years. Grafting is an important technique for its cultivation. For a successful grafting, graft union development generally involves the formation of callus and vascular bundles at the graft union. To explore the molecular mechanism of graft union development, we applied high throughput RNA sequencing to investigate the transcriptomic profiles of graft union at four timepoints (0 days, 8 days, 15 days, and 30 days) during the pecan grafting process. After de novo assembly, 83,693 unigenes were obtained, and 40,069 of them were annotated. A total of 12,180 differentially expressed genes were identified between by grafting. Genes involved in hormone signaling, cell proliferation, xylem differentiation, cell elongation, secondary cell wall deposition, programmed cell death, and reactive oxygen species (ROS) scavenging showed significant differential expression during the graft union developmental process. In addition, we found that the content of auxin, cytokinin, and gibberellin were accumulated at the graft unions during the grafting process. These results will aid in our understanding of successful grafting in the future.