Verification of the Interaction Target Protein of the Effector ApCE22 of Arthrinium phaeospermum in Bambusa pervariabilis × Dendrocalamopsis grandis.

The study of interaction proteins of the pathogen A. phaeospermum effector protein is an important means to analyze the disease-resistance mechanism of Bambusa pervariabilis × Dendrocalamopsis grandis shoot blight. To obtain the proteins interacting with the effector ApCE22 of A. phaeospermum, 27 proteins interacting with the effector ApCE22 were initially identified via a yeast two-hybrid assay, of which four interaction proteins were obtained after one-to-one validation. The B2 protein and the chaperone protein DnaJ chloroplast protein were then verified to interact with the ApCE22 effector protein by bimolecular fluorescence complementation and GST pull-down methods. Advanced structure prediction showed that the B2 protein contained the DCD functional domain related to plant development and cell death, and the DnaJ protein contained the DnaJ domain related to stress resistance. The results showed that both the B2 protein and DnaJ protein in B. pervariabilis × D. grandis were the target interaction proteins of the ApCE22 effector of A. phaeospermum and related to the stress resistance of the host B. pervariabilis × D. grandis. The successful identification of the pathogen effector interaction target protein in B. pervariabilis × D. grandis plays an important role in the mechanism of pathogen-host interaction, thus providing a theoretical basis for the control of B. pervariabilis × D. grandis shoot blight.

Genome-Wide Identification and Characterization of R2R3-MYB Provide Insight into Anthocyanin Biosynthesis Regulation Mechanism of Ananas comosus var. bracteatus.

The R2R3-MYB proteins comprise the largest class of MYB transcription factors, which play an essential role in regulating anthocyanin synthesis in various plant species. Ananas comosus var. bracteatus is an important colorful anthocyanins-rich garden plant. The spatio-temporal accumulation of anthocyanins in chimeric leaves, bracts, flowers, and peels makes it an important plant with a long ornamental period and highly improves its commercial value. We conducted a comprehensive bioinformatic analysis of the R2R3-MYB gene family based on genome data from A. comosus var. bracteatus. Phylogenetic analysis, gene structure and motif analysis, gene duplication, collinearity, and promoter analysis were used to analyze the characteristics of this gene family. In this work, a total of 99 R2R3-MYB genes were identified and classified into 33 subfamilies according to phylogenetic analysis, and most of them were localized in the nucleus. We found these genes were mapped to 25 chromosomes. Gene structure and protein motifs were conserved among AbR2R3-MYB genes, especially within the same subfamily. Collinearity analysis revealed four pairs of tandem duplicated genes and 32 segmental duplicates in AbR2R3-MYB genes, indicating that segmental duplication contributed to the amplification of the AbR2R3-MYB gene family. A total of 273 ABRE responsiveness, 66 TCA elements, 97 CGTCA motifs, and TGACG motifs were the main cis elements in the promoter region under response to ABA, SA, and MEJA. These results revealed the potential function of AbR2R3-MYB genes in response to hormone stress. Ten R2R3-MYBs were found to have high homology to MYB proteins reported to be involved in anthocyanin biosynthesis from other plants. RT-qPCR results revealed the 10 AbR2R3-MYB genes showed tissue-specific expression patterns, six of them expressed the highest in the flower, two genes in the bract, and two genes in the leaf. These results suggested that these genes may be the candidates that regulate anthocyanin biosynthesis of A. comosus var. bracteatus in the flower, leaf, and bract, respectively. In addition, the expressions of these 10 AbR2R3-MYB genes were differentially induced by ABA, MEJA, and SA, implying that these genes may play crucial roles in hormone-induced anthocyanin biosynthesis. Our study provided a comprehensive and systematic analysis of AbR2R3-MYB genes and identified the AbR2R3-MYB genes regulating the spatial-temporal anthocyanin biosynthesis in A. comosus var. bracteatus, which would be valuable for further study on the anthocyanin regulation mechanism of A. comosus var. bracteatus.

Differential Metabolomics Reveals Pathogenesis of Pestalotiopsis kenyana Causing Leaf Spot Disease of Zanthoxylum schinifolium.

Pepper leaf spot is a common disease of Zanthoxylum schinifolium. When it is serious, it directly affects the growth of Z. schinifolium, making the plant unable to blossom and bear fruit, which seriously restricts the development of the Z. schinifolium industry. Therefore, the pathogenic mechanism of leaf spots should be explored to provide a basis for a comprehensive understanding of the disease. Using liquid chromatography-mass spectrometry (LC-MS) technology combined with the data-dependent acquisition, the full spectrum analysis of pathogen mycelium samples was carried out. Partial least squares discriminant analysis (PLS-DA) was used to reveal the differences in metabolic patterns among different groups. Hierarchical clustering analysis (HCA) and PLS-DA were used to reveal the relationship between samples and metabolites, which reflected the metabolomics changes of Pestalotiopsis kenyana in the logarithmic growth phase of mycelia, the stable growth phase of mycelia, the massive spore stage, the induction culture conditions of PDA and Z. schinifolium leaves, and the possible pathogenic substances were selected for pathogenicity detection. PLS-DA had a strong predictive ability, indicating a clear analysis trend between different groups. The results of the metabolomics analysis showed that the differential metabolites of pathogenic bacteria were abundant at different stages and under different medium conditions, and the content of metabolites changed significantly. There were 3922 differential metabolites in nine groups under positive and negative ion modes, including lipids and lipid molecules, organic acids and their derivatives, organic heterocyclic compounds, organic oxygen compounds, carbohydrate polyketides, nucleosides, nucleotides, and analogs. The results of the pathogenicity test showed that the leaves treated with 3,5-dimethoxy benzoic acid, S-(5-adenosy)-l-homocysteine, 2-(1H-indol-3-yl) acetic acid, l-glutamic acid, and 2-(2-acetyl-3,5-dihydroxy phenyl) acetic acid showed different degrees of yellowish-brown lesions. This indicated that these substances may be related to the pathogenicity of P. kenyana, and the incidence was more serious when treated with 3,5-dimethoxybenzoic acid and S-(5-adenosy)- l -homocysteine. This study provides a basis for further analysis of differential metabolites and provides a theoretical reference for the prevention and treatment of Z. schinifolium leaf spot.

Adventitious root primordia formation and development in the stem of Ananas comosus var. bracteatus slip.

There are about 4-6 slips on a fruit, and they are good materials for effective regeneration of Ananas comosus var. bracteatus. Adventitious root (AR) induction is essential for the propagation of Ananas comosus var. bracteatus slips. Growth regulator treatment, and culture medium are imperative factors that affect slip growth and rooting. In order to screen the optimal methods for slips rooting and reveal the anatomic procedure of slip rooting, this study induced slip rooting by different treatment of growth regulator, culture medium, observed the slip stem structure, AR origination and formation procedure through paraffin sections. The results showed that, slip cuttings treated with 100 mg/L of Aminobenzotriazole (ABT) for 6 hrs, cultured in river sand: coconut chaff: garden soil 2:2:1 medium is the optimal method for rooting. The proper supplementary of ABT can enhance the soluble sugar content, soluble protein content, polyphenol oxidase (PPO) activity and peroxidase (POD) enzyme activity, which resulted in the improvement of rooting. The slip stem structure is quite different from other monocots, which consists of epidermis, cortex, and stele with vascular tissues distributed in the cortex and stele. The AR primordia originates from the parenchyma cells located on the borderline between the cortex and stele. The vascular tissues in the AR develop and are connected with vascular tissue of the stem before the AR grew out the stem. The number of primary xylem poles in AR is about 30.

MicroRNAs Roles in Plants Secondary Metabolism.

Plant growth and development is dependent on the regulation of classes of microRNAs (miRNAs) that have emerged as important gene regulators. These miRNAs can regulate plant gene expression to function. They play an important roles in biological homeostasis and environmental response controls. A wide range of plant biological and metabolic processes, including developmental timing, tissues specific development, and differentiation, depends on miRNAs. They perpetually regulate secondary metabolite functions in different plant family lines. Mapping of molecular phylogenies shows the distribution of secondary metabolism in the plant territory. More importantly, a lot of information related to miRNA regulatory processes in plants is revealed, but the role of miRNAs in secondary metabolism regulation and functions of the metabolites are still unclear. In this review, we pinnacle some potential miRNAs regulating the secondary metabolite biosynthesis activities in plants. This will provide an alternative knowledge for functional studies of secondary metabolism.

AbhemC encoding porphobilinogen deaminase plays an important role in chlorophyll biosynthesis and function in albino Ananas comosus var. bracteatus leaves.

BACKGROUND: The chimeric leaves of Ananas comosus var. bracteatus are composed of normal green parts (Grs) and albino white parts (Whs). Although the underlying mechanism of albinism in A. comosus var. bracteatus leaves is not fully understood, it is likely associated with the chlorophyll (Chl) biosynthesis. In this biosynthetic process, porphobilinogen deaminase (PBGD) plays a crucial role by catalyzing the conversion of porphobilinogen (PBG) to uroporphyrinogen III (Urogen III). Therefore, its encoding gene AbhemC was investigated here in association with Chl biosynthesis and albinism in chimeric A. comosus var. bracteatus leaves. METHODS: The Chl content, main Chl biosynthesis precursor content, and main enzyme activity were determined and compared between the Whs and Grs of A. comosus var. bracteatus leaves. In addition, AbhemC was cloned and its transcriptional expression and prokaryotic protein expression were analyzed. Furthermore, RNAi-mediated silencing of AbhemC was produced and assessed in tobacco plants. RESULTS: The concentration of Chl a and Chl b in the Grs was significantly higher than that in the Whs, respectively. Additionally, the content of the Chl biosynthesis precursor Urogen III decreased significantly in the Whs compared with the Grs. Thus, the transition of PBG to Urogen III may be the first rate-limiting step leading to albinism in the chimeric leaves of A. comosus var. bracteatus. The gene AbhemC comprised 1,135 bp and was encoded into a protein with 371 amino acids; phylogenetically, AbhemC was most closely related to hemC of pineapple. Prokaryotic expression and in vitro enzyme activity analysis showed that the cloned mRNA sequence of AbhemC was successfully integrated and had PBGD activity. Compared with control plants, transgenic tobacco leaves with pFGC5941-AbhemC-RNAi vector were substantially less green with significantly reduced hemC expression and Chl content, as well as reduced PBGD enzyme activity and significantly decreased content of Chl biosynthesis precursors from Urogen III onwards. Our results suggest that the absence of hemC expression reduces the enzyme activity of PBGD, which blocks the transition of PBG to Urogen III, and in turn suppresses Chl synthesis leading to the pale-green leaf color. Therefore, we suggest that AbhemC plays an important role in Chl synthesis and may be an important factor in the albinism of A. comosus var. bracteatus leaves.