Summary: Plant growth‐promoting rhizobacteria are involved in altering secondary root (SR) formation, but hitherto there has been no distinction between the different types of SRs upon induction of soil biota, and the genetic pathways involved. By using plate and soil systems, we studied the effects of the Pseudomonas strains CM11 and WCS417 on plant performance with a focus on root development. Through a combination of cellular, molecular and genetic analyses, we investigated the type of SRs induced upon CM11 and WCS417 root inoculation using genetic pathways associated with specific SR types. CM11 was shown to affect the root architecture differently from WCS417. CM11 inoculation leads to primary root arrest, whereas WCS417 reveals a longer primary root. Both CM11 and WCS417 activate the PLETHORA 3,5,7‐controlled lateral root pathway, rather than the WUSCHEL‐RELATED HOMEOBOX 11,12‐controlled adventitious (lateral) root pathway. In addition, CM11 promotes plant growth in model and various crop species. It improves plant fitness traits, such as bigger shoots, faster bolting and higher yield in terms of seeds. Our results indicate that the root system architecture can be promoted by activation of PLETHORA 3,5,7 dependent primed lateral pre‐branch sites upon inoculation with CM11, which creates great potential to gain a better understanding of root plasticity.

Cold stress, triggered by particularly low temperatures, is one of the most severe forms of abiotic stress in pepper plants and a major constraint to the global pepper industry, threatening crop production and food security. To acclimatize to extreme conditions, the plant undergoes numerous modifications, including genetic and metabolic modulations. A thorough study of both the genetic and metabolic alterations of plants in response to cold stress is vital to understanding and developing the cold stress resistance mechanism. This study implemented transcriptome and metabolome analyses to evaluate the cold stress response in cold-tolerant and cold-sensitive pepper species. The weighted gene co-expression network revealed three significant modules related to cold stress tolerance in Capsicum pubescens. We identified 17 commonly enriched genes among both species at different time points in 10 different comparisons, including the AP2 transcription factor, LRR receptor-like serine, hypersensitivity-related 4-like protein, and uncharacterized novel.295 and novel.6172 genes. A pathway enrichment analysis indicated that these DEGs were mainly associated with the MAPK signaling pathway, hormone signaling pathway, and primary and secondary metabolism. Additionally, 21 significantly differentially accumulated metabolites (DAMs) were identified in both species after 6 h of cold stress. A transcriptome and metabolome integrated analysis revealed that 54 genes correlated with metabolites enriched in five different pathways. Most genes and metabolites involved in carbohydrate metabolism, the TCA cycle, and flavonoid biosynthesis pathways were upregulated in cold-tolerant plants under cold stress. Together, the results of this study provide a comprehensive gene regulatory and metabolic network in response to cold stress and identified some key genes and metabolic pathways involved in pepper cold tolerance. This study lays a foundation for the functional characterization and development of pepper cultivars with improved cold tolerance.

Radish is a crucial vegetable crop of the Brassicaceae family with many varieties and large cultivated area in China. Radish is a cool season crop, and there are only a few heat tolerant radish varieties in practical production with little information concerning the related genes in response to heat stress. In this work, some physiological parameter changes of young leaves under short-term heat stress were detected. Furthermore, we acquired 1802 differentially expressed mRNAs (including encoding some heat shock proteins, heat shock factor and heat shock-related transcription factors), 169 differentially expressed lncRNAs and three differentially expressed circRNAs (novel_circ_0000265, novel_circ_0000325 and novel_circ_0000315) through strand-specific RNA sequencing technology. We also found 10 differentially expressed miRNAs (ath-miR159b-3p, athmiR159c, ath-miR398a-3p, athmiR398b-3p, ath-miR165a-5p, ath-miR169g-3p, novel_86, novel_107, novel_21 and ath-miR171b-3p) by small RNA sequencing technology. Through function prediction and enrichment analysis, our results suggested that the significantly possible pathways/complexes related to heat stress in radish leaves were circadian rhythm-plant, photosynthesis—antenna proteins, photosynthesis, carbon fixation in photosynthetic organisms, arginine and proline metabolism, oxidative phosphorylation, peroxisome and plant hormone signal transduction. Besides, we identified one lncRNA–miRNA–mRNAs combination responsive to heat stress. These results will be helpful for further illustration of molecular regulation networks of how radish responds to heat stress.

Background: Anthocyanins have distinct biological functions in plant coloring, plant defense against strong light, UV irradiation, and pathogen infection. Aromatic hydroxyl groups and ortho-dihydroxyl groups in anthocyanins are able to inhibit free-radical chain reactions and hydroxyl radicals. Thus, anthocyanins play an antioxidative role by removing various types of ROS. Pepper is one of the solanaceous vegetables with the largest cultivation area in China. The purple-fruited pepper is rich in anthocyanins, which not only increases the ornamental nature of the pepper fruit but also benefits the human body. In this experiment, light-induced regulatory pathways and related specific regulators of anthocyanin biosynthesis were examined through integrative transcriptomic and metabolomic analysis. Results: Results revealed that delphinium 3-O-glucoside significantly accumulated in light exposed surface of pepper fruit after 48 h as compared to shaded surface. Furthermore, through strand-specific sequencing technology, 1341 differentially expressed genes, 172 differentially expressed lncRNAs, 8 differentially expressed circRNAs, and 28 differentially expressed miRNAs were identified significantly different among both surfaces. The flavonoid synthesis pathway was significantly enriched by KEGG analysis including SHT (XM_016684802.1), AT-like (XM_016704776.1), CCoAOMT (XM_016698340.1, XM_016698341.1), CHI (XM_016697794.1, XM_016697793.1), CHS2 (XM_016718139.1), CHS1B (XM_016710598.1), CYP98A2-like (XM_016688489.1), DFR (XM_016705224.1), F3’5’H (XM_016693437.1), F3H (XM_016705025.1), F3’M (XM_016707872.1), LDOX (XM_016712446.1), TCM (XM_016722116.1) and TCM-like (XM_016722117.1). Most of these significantly enriched flavonoid synthesis pathway genes may be also regulated by lncRNA. Some differentially expressed genes encoding transcription factors were also identified including MYB4-like (XM_016725242.1), MYB113-like (XM_016689220.1), MYB308-like (XM_016696983.1, XM_016702244.1), and EGL1 (XM_016711673.1). Three ‘lncRNA-miRNA-mRNA’ regulatory networks with sly-miR5303, stu-miR5303g, stu-miR7997a, and stu-miR7997c were constructed, including 28 differentially expressed mRNAs and 6 differentially expressed lncRNAs. Conclusion: Possible light regulated anthocyanin biosynthesis and transport genes were identified by transcriptome analysis, and confirmed by qRT-PCR. These results provide important data for further understanding of the anthocyanin metabolism in response to light in pepper.

Pepper is an important vegetable in the world. In this work, mRNA and ncRNA transcriptome profiles were applied to understand the heterosis effect on the alteration in the gene expression at the seedling and flowering stages between the hybrid and its parents in Capsicum chinense. Our phenotypic data indicated that the hybrid has dominance in leaf area, plant scope, plant height, and fruit-related traits. Kyoto Encyclopedia of Genes and Genomes analysis showed that nine members of the plant hormone signal transduction pathway were upregulated in the seedling and flowering stages of the hybrid, which was supported by weighted gene coexpression network analysis and that BC332_23046 (auxin response factor 8), BC332_18317 (auxin-responsive protein IAA20), BC332_13398 (ethylene-responsive transcription factor), and BC332_27606 (ethylene-responsive transcription factor WIN1) were candidate hub genes, suggesting the important potential role of the plant hormone signal transduction in pepper heterosis. Furthermore, some transcription factor families, including bHLH, MYB, and HSF were greatly over-dominant. We also identified 2,525 long ncRNAs (lncRNAs), 47 micro RNAs (miRNAs), and 71 circle RNAs (circRNAs) in the hybrid. In particular, downregulation of miR156, miR169, and miR369 in the hybrid suggested their relationship with pepper growth vigor. Moreover, we constructed some lncRNA–miRNA–mRNA regulatory networks that showed a multi-dimension to understand the ncRNA relationship with heterosis. These results will provide guidance for a better understanding of the molecular mechanism involved in pepper heterosis.