Tropical Plant Biology

Li, Hu; Yang, Xin; Niyitanga, Sylvain; He, Qinyao; Chen, Siyuan; Xu, Jiantang; Qi, Jianmin; Tao, Aifen; Fang, Pingping; Zhang, Liwu

2022 Tropical Plant Biology

doi: 10.1007/s12042-022-09320-y

Kenaf (Hibiscus cannabinus L.) is one of the most important bast fiber crops. And the MYB transcription factor plays a vital role in plant development regulation. In this study, the transcriptome data of 9 tissues of kenaf was analyzed deeply. The differentially expressed genes (DEGs) between stem bark at 60 days after sowing (DAS) and other tissues were screened out and the number of overlapping DEGs between different groups varied greatly. Interestingly, plenty of MYB transcription factors were identified among these overlapping DEGs suggesting that these genes may be related to the growth of stem bark and need to be further characterized. Totally, 353 HcMYBs were identified from the whole genome and classified into four groups: 1R-MYB, 2R-MYB, 3R-MYB, and 4R-MYB, with 1R-MYB and 2R-MYB accounting for the majority. Phylogenetic analysis revealed that members of the 1R-MYB and 2R-MYB families were divided into 12 and 37 subgroups. Synteny analysis indicated that segmental and tandem duplication events played a key role in the expansion of the MYB gene family in kenaf. Analysis of the HcMYB expression patterns in various tissues or developmental stages led to the screening of numerous HcMYB, including HcMYB92, HcMYB162, HcMYB143, and HcMYB213, which may have the ability to influence stem bark development. The sole HcMYB identified by Weighted Gene Co-Expression Network Analysis (WGCNA) in the stem bark at 60 DAS module, HcMYB207, co-expressed with a large number of genes with various functions. These findings might provide valuable information for further research on the potential function of HcMYBs.

Xu, Yongju; Zhang, Xiaojun; Hou, Rui; Zhang, Xiaohong; Li, Shuang; Yue, Fuliang; Zhang, Xiangqiong; Zhu, Xunlu

2022 Tropical Plant Biology

doi: 10.1007/s12042-022-09321-x

Stem rot, caused by soilborne pathogen Sclerotium rolfsii, is one of the most destructive diseases of peanut (Arachis hypogaea L.) worldwide. Although microRNAs (miRNAs) are indispensable regulators for plant defense, the miRNA species have not been explored for peanut immunity against the soilborne pathogen Sclerotium rolfsii. Here, we report a miRNA comparative analysis of the durably resistant peanut variety Rizhaohua-1 (Rzh) and the susceptible peanut variety Jitian-1 (JT) in response to infection by Sclerotium rolfsii. We identified a group of known and novel miRNAs that were differentially expressed upon S. rolfsii infection. The predicted target genes included receptor kinases, transcription factors, and genes involved in the production and transport of metabolites. In this study, we have shown that miRNAs regulate a broad range of genes to respond to the pathogen, and eventually establish a systemic defense network to combat disease.

Koetle, Motselisi Jane; Snyman, Sandra Jane; Rutherford, Richard Stuart

2022 Tropical Plant Biology

doi: 10.1007/s12042-022-09323-9

The present study evaluated the drought tolerance potential of ten epimutants generated in vitro via 5-Azacytidine (Azac) demethylation, followed by re-methylation in the presence of imidacloprid (IMI), both under polyethylene glycol (PEG) osmotic pressure and heat stress. Ex vitro chimera dissolution involved four rounds of repeated drought stress in the glasshouse. Most epimutant lines had significantly high Fv/Fm values (up to 0.46, 0.76, and 0.78 respectively for V2, V3 and V4 stress rounds) when compared with the stressed parent cultivar N41 control (S N41) with 0.12, 0.21, and 0.59 ratios respectively. Significant rapid growth rates (0.25 cm height increase per day) were observed in the GP4, MP1, MP5, and SP5 lines while S N41 had 0.10 cm stalk height gain per day during stress. Moreover, the percent green leaf area (GLA) values were higher (57.2–73.0%) for the epimutant lines than drought sensitive MP6 (12.4%) and S N41 (47.3%) during stress. The GP1, MP5 and SP5 lines maintained high relative water content (43–51%) than S N41 (38%) under drought conditions. Principal component and cluster analyses of morpho-physiological traits separated trait indices data and revealed that the epimutants with highest drought stress tolerance were the MP2, MP5, GP2, GP4, GP5, and SP5, and these same lines recuperated rapidly from stress. This study has laid a foundation for an alternative method of assessing sugarcane phenotypes for drought tolerance using morpho-physiological traits.

Chen, Huafeng; Qin, Lei; Tian, Jinge; Wang, Xianglan

2022 Tropical Plant Biology

doi: 10.1007/s12042-022-09324-8

GOLDEN 2-LIKE (GLK) transcription factors are members of the GARP superfamily and are involved in chloroplast development and stress tolerance. These transcription factors have been studied at the genome level across several plant species. However, no study has comprehensively analyzed the GLK family in foxtail millet (Setaria italica L.). The present study discovered 59 GLK genes in foxtail millet. Multiple sequence alignment and gene motif analysis revealed the presence of Myb-SHAQKYF and Myb-CC-LHEQLE motifs in all the members. In addition, the gene promoters mainly had light- and stress-responsive cis-regulatory elements. Syntenic analysis showed that whole-genome duplications (WGD) and dispersed duplications contributed to the expansion of the SiGLK gene family. Gene expression analysis revealed that SiGLKs exhibited preferential expression in bundle sheath than in the mesophyll cells. Meanwhile, analyzing these genes in foxtail millet under abiotic stress demonstrated a significant role for SiGLK30, 38, 48, and 52 in regulating salt, cold, and drought stress responses. Finally, qRT-PCR confirmed that cold stress increased SiGLK52 and SiGLK31 expression. The study thus provides an overview of GLK gene evolution in foxtail millet and a clue to its function in bundle sheath and mesophyll cell and stress tolerance.

Cavalcante, Brayan Paiva; Silva, Kleber Resende; de Souza, Everton Hilo; Versieux, Leonardo M.; Martinelli, Adriana Pinheiro

2022 Tropical Plant Biology

doi: 10.1007/s12042-022-09325-7

Hohenbergia is one the most diverse genera in Bahia state, and inhabits almost all regions of the state. As a result of ongoing studies on Hohenbergia in Bahia, Brazil, here we describe and illustrate Hohenbergia erecta, endemic to the municipality of Mucugê, at Chapada Diamantina. Hohenbergia erecta differs from its morphologically related, H. catingae, by an elongated tubular rosette (vs short stem with a crateriform rosette), and a once-branched cylindrical inflorescence (vs 2–3-branched pyramidal inflorescence), with branches congested at the apex (vs branches laxly arranged). Due to a small distribution area in the Caatinga forest and based on a spatial analysis we categorized it as Endangered (EN), following the IUCN criteria. Hohenbergia erecta is endemic to the central region of Chapada Diamantina, dominant in the area, where no other known Hohenbergia species have been found sympatrically. It is important, however, that new field expeditions are conducted in the region to observe the richness of the genus at Chapada Diamantina.

Valenzuela-Apodaca, Juan P.; Cruz-Mendívil, Abraham; Gaytán-Pinzón, Grethel P.; Rodríguez-González, Hervey; Peinado-Fuentes, Luis A.; Sandoval-Castro, Eduardo; Calderón-Vázquez, Carlos L.

2022 Tropical Plant Biology

doi: 10.1007/s12042-022-09326-6

Genes related to oil and protein accumulation have been identified in maize, however, many loci underlying the variation in these traits are still unidentified. In this study, 49 doubled haploids (DH) lines derived from subtropical maize recombinant populations were genotyped through DArTSeq technology, resulting in 29,398 single nucleotide polymorphisms (SNPs), of which 20,202 markers with minor allele frequency > 0.05 were kept. Oil content in DH lines ranged from 4 to 8.3%, whereas protein content ranged from 8.44 to 15.63%. A genome-wide association study (GWAS) was conducted to detect significant SNPs associated with oil and protein content. The physical position of SNPs was mapped and a 100-kb window surrounding the significant SNPs was scanned to identify genes associated with the phenotype. Three significant SNPs were close to genes related to oil accumulation, and one was close to a gene related to protein accumulation. The favorable alleles for the SNPs 5589069 (A/G), 100156460 (C/T), and 2412207 (G/T) were present in 70.9%, 35.4%, and 22.5% of the DH lines with high oil (> 6%) content (HOC), respectively. The favorable allele (A/G) for SNP 5586538 was present in 14.63% of the DH lines with high protein (> 10%) content (HPC). Once the favorable alleles were detected, a genotyping validation by High-Resolution Melting (HRM) technique was performed, showing similarity rates with DArTSeq between 56% and 78.9% for the assayed SNPs. These novel SNPs could be useful for further marker-assisted breeding of HOC or HPC in subtropical maize.