Kenaf is an annual bast fiber crop. Drought stress influences the growth of kenaf stems and causes a marked decrease in fiber yield and quality. Research on the drought resistance of kenaf is therefore important, but limited information is available on the response mechanism of kenaf to drought stress. In this study, a transcriptome analysis of genes associated with the drought stress response in kenaf was performed. About 264,244,210 bp high-quality reads were obtained after strict quality inspection and data cleaning. Compared with the control group, 4,281 genes were differentially expressed in plants treated with drought stress for 7 d (the drought stress group). Compared with the control group, 605 genes showed differential expression in plants subjected to drought stress for 6 d and then watered for 1 d (the rewatering group). Compared with the rewatering group, 5,004 genes were differentially expressed in the drought stress group. In the comparisons between the drought stress and control groups, and between the drought stress and rewatering groups, the pathway that showed the most highly significant enrichment was plant hormone signal transduction. In the comparison between the rewatering and control groups, the pathways that showed the most highly significant enrichment were starch and sucrose metabolism. Eight transcription factors belonging to the AP2/ERF, MYB, NAC, and WRKY families (two transcription factors per family) detected in the leaf transcriptome were associated with the drought stress response. The identified transcription factors provide a basis for further investigation of the response mechanism of kenaf to drought stress. . 2008. Role of the Arabidopsis thaliana NAC transcription factors ANAC019 and ANAC055 in regulating jasmonic acid-signaled defense responses. X. 2016. Insight into the AP2/ERF transcription factor superfamily in sesame and expression profiling of DREB subfamily under drought stress. BMC Plant Biology 16:171 L. 2006. Overexpressing a NAM, ATAF, and CUC (NAC) transcription factor enhances drought resistance and salt tolerance in rice. Martinoia E. 2004. Disruption of AtMRP4, a guard cell plasma membrane ABCC-type ABC transporter, leads to deregulation of stomatal opening and increased drought susceptibility.
Heavy metal contamination of soils has become a serious global issue, and bioremediation has been proposed as a potential solution. Kenaf (Hibiscus cannabinus L.) is a fast growing, non-woody multipurpose annual plant that is suitable for removing excess heavy metals from soils. However, there has been relatively little research on the kenaf molecular mechanisms induced in response to an exposure to heavy metal stress. Thus, whole kenaf seedlings grown under control (normal) and stress (plumbic treatment) conditions were sampled for transcriptome sequencing. Unigenes generated through the de novo assembly of clean reads were functionally annotated based on seven databases. Transcription factor (TF)-coding genes were predicted and the physiological traits of the seedlings were analyzed. A total of 44.57 Gb high-quality sequencing data were obtained, which were assembled into 136,854 unigenes. These unigenes included 1,697 that were regarded as differentially expressed genes (DEGs). A GO enrichment analysis of the DEGs indicated that many of them are related to catalytic activities. Moreover, the DEGs appeared to suggest that numerous KEGG pathways are suppressed (e.g., the photosynthesis-involving pathways) or enhanced (like the flavonoid metabolism pathways) in response to Pb stress. Of the 2,066 predicted TF-coding genes, only 55 were differentially expressed between the control and stressed samples. Further analyses suggested that the plumbic stress treatment induced reactive oxygen species-dependent programmed cell death in the kenaf plants via a process that may be regulated by the differentially expressed NAC TF genes.
Many Anoectochilus plants are now facing extinction; hence, they are propagated mainly from tissue culture. However, growth performance and secondary metabolites have not been fully identified on tissue-cultured plantlets from multiple Anoectochilus species under shading. In the present study, five Anoectochilus species [A. roxburghii (Wall.) Lindl., Fu_1; A. koshuaensis Hayata, Fu_2; A. formosanus Hayata, Tai; unidentified species of Fu_New_1 and Fu_New_2] were generated from micropropagated plantlets and cultured under shade treatments of three levels (mean light intensities: mild, *2000 Lx; medium, *800 Lx; intensive, *440 Lx) for five months. Among the five Anoectochilus species, the Tai and Fu_New_1 species had the highest survival rate and the Tai species had the best performance of stem morphology and foliar kaempferol content in the medium shade treatment, but it had fewer leaves and lower ratio of quercetin/ kaempferol than the Fu_1 species. The Fu_New_2 species had the greatest biomass accumulation and highest content of total flavonoids, especially under the mild shade treatment. Therefore, among the Anoectochilus species tested in this study, A. formosanus is suggested to be used in continuous propagation, A. roxburghii is suggested to be planted in stressed environment, and the new species of Fu_New_2 is suggested to be planted for the production of flavonoids. Mild and medium levels of shading are suggested to be used when biomass production and fast growing are needed for Anoectochilus plantlets, respectively.
Recent research progresses on tissue culture (e.g. fast reproduction, another culture, protoplast culture and organogenesis) and genetic transformation of kenaf were reviewed and summarized in this paper. Existing problems were discussed, aiming to provide scientific references for promoting tissue culture and genetic transformation of kenaf.
The molecular mechanisms that underlie drought stress responses in kenaf, an important crop for the production of natural fibers, are poorly understood. To address this issue, we describe here the first iTRAQ ‐based comparative proteomic analysis of kenaf seedlings. Plants were divided into the following three treatment groups: Group A, watered normally (control); Group B, not watered for 6 days (drought treatment); and Group C, not watered for 5 days and then rewatered for 1 day (recovery treatment). A total of 5014 proteins were detected, including 4932 (i.e., 98.36%) that were matched to known proteins in a BLAST search. We detected 218, 107, and 348 proteins that were upregulated in Group B compared with Group A, Group C compared with Group A, and Group B compared with Group C, respectively. Additionally, 306, 145, and 231 downregulated proteins were detected during the same comparisons. Seventy differentially expressed proteins were analyzed and classified into 10 categories: photosynthesis, sulfur metabolism, amino sugar and nucleotide sugar metabolism, oxidative phosphorylation, ribosome, fatty acid elongation, thiamine metabolism, tryptophan metabolism, plant–pathogen interaction, and propanoate. Kenaf adapted to stress mainly by improving the metabolism of ATP , regulating photosynthesis according to light intensity, promoting the synthesis of osmoregulators, strengthening ion transport signal transmission, and promoting metabolism and cell stability. This is the first study to examine changes in protein expression in kenaf plants exposed to drought stress. Our results identified key drought‐responsive genes and proteins and may provide useful genetic information for improving kenaf stress resistance.
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