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Radish (Raphanus sativus L.) is an important root vegetable crop that is easily infected by various pathogens that result in decreased yield and quality. Nucleotide-binding site and leucine-rich repeat (NBS-LRR) genes play vital roles in resisting pathogen infection in plants. However, the genome-wide characterization and functional roles of NBS-LRR genes remain largely unexplored in radish. Here, a total of 187 RsNBS-LRR genes were identified at the whole-genome level in radish, among which 80 RsNBS-LRR genes were unevenly distributed on nine radish chromosomes. Interestingly, 15 clusters containing 36 RsNBS-LRR genes occurred in eight chromosomes. RNA-Seq data showed that several RsNBS-LRR genes exhibited significant differential expression profiles in different radish tissues. Moreover, a range of cis-acting regulatory elements associated with ABA, MeJA, or SA were identified in the promoter region of some RsNBS-LRR genes. RT-qPCR analysis showed that the expression of a few RsNBS-LRR genes (e.g., RsNBS021 and RsNBS163) was significantly induced under Peronospora parasitica infection and/or ABA treatment, indicating that they might play critical roles in ABA-dependent defense resistance processes. These results could enhance our understanding of the evolutionary relationship of RsNBS-LRR genes and facilitate the genetic manipulation of disease resistance in radish breeding programs. [ABSTRACT FROM AUTHOR]

Basic leucine zipper (bZIP) transcription factors play crucial roles in various abiotic stress responses as well as anthocyanin accumulation. Anthocyanins are most abundant in colorful skin radish, which exhibit strong antioxidant activity that offers benefits for human health. Here, a total of 135 bZIP-encoding genes were identified from radish genome. Synteny analysis showed that 104 radish and 63 ArabidopsisbZIP genes were orthologous. Transcriptome analysis revealed that 10 RsbZIP genes exhibited high-expression levels in radish taproot (RPKM>10). Specifically, RsbZIP010 exhibited down-regulated expression under Cd, Cr and Pb stresses, whereas RsbZIP031 and RsbZIP059 showed significant down-regulation under heat and salt stresses, respectively. RT-qPCR analysis indicated that RsbZIP011 and RsbZIP102 were significantly up-regulated in the tissues of radish with high anthocyanin contents. Furthermore, the promoter sequences of 39 anthocyanin-related genes were found to contain G-box or ACE-box elements that could be recognized by bZIP family members. Taken together, several RsbZIPs might be served as critical regulators in radish taproot under Cd, Cr, Pb, heat and salt stresses. RsbZIP011 and RsbZIP102 were the potential participants in anthocyanin biosynthesis pathway of radish. These results facilitate further investigation on functional characterization of bZIP genes in response to abiotic stress and anthocyanin biosynthesis in radish. [ABSTRACT FROM AUTHOR]

Main conclusion Among 247 RsAP2/ERF identified, the majority of the 21 representatives were preferably expressed under drought and heat while suppressed under heavy metals, indicating their potential roles in abiotic stress responses and tolerance. APETALA2/Ethylene-Responsive factor (AP2/ERF) transcription factor (TF) is one of the largest gene families in plants that play a fundamental role in growth and development as well as biotic and/or abiotic stresses responses. Although AP2/ERFs have been extensively characterized in many plant species, little is known about this family in radish, which is an important root vegetable with various medicinal properties. The available genome provides valuable opportunity to identify and characterize the global information on AP2/ERF TFs in radish. In this study, a total of 247 ERF family genes were identified from the radish genome, and sequence alignment and phylogenetic analyses classified the AP2/ERF superfamily into five groups (AP2, ERF, DREB, RAV and soloist). Motif analysis showed that other than AP2/ERF domains, other conserved regions were selectively distributed among different clades in the phylogenetic tree. Chromosome location analysis showed that tandem duplication may result in the expansion of RsAP2/ERF gene family. The RT-qPCR analysis confirmed that a proportion of AP2/ERF genes were preferably expressed under drought and heat stresses, whereas they were suppressed under the ABA and heavy metal stresses. These results provided valuable information for further evolutionary and functional characterization of RsAP2/ERF genes, and contributed to genetic improvement of stress tolerances in radish and other root vegetable crops. • Totally 247 AP2-ERF genes were firstly genome-widely identified in radish. • The AP2/ERF superfamily could be classified into five groups. • Tandem duplications play critical role in the expansion of RsAP2/ERF genes. • A proportion of AP2/ERF genes were differentially expressed under abiotic stresses. [ABSTRACT FROM AUTHOR]

Radish (Raphanus sativus L.) is an important worldwide root vegetable crop. Little information of the GRAS gene family was available in radish. Herein, a total of 51 GRAS family members were firstly identified from radish genome, and unevenly located onto nine radish chromosomes. Expression analysis of RsGRAS genes in taproot displayed that RsSCL15a and RsSHRc were highly expressed in the radish cambium, and its expression level was increased with the taproot thickening. Comparative transcriptome analysis revealed that the expression patterns of RsGRAS genes varied upon exposure to different abiotic stresses including heavy metals, salt and heat. The expression level of six RsGRAS genes including RsSHRc was increased under chilling stress in two radish genotypes with different cold tolerance. Further analysis indicated that RsGRAS genes could respond to cold stress rapidly and the expression of RsSHRc was up-regulated at different development stages (cortex splitting and thickening stages) under long-term cold treatment. Transient expression of RsSHRc gene in radish showed that RsSHRc possessed the reliable function of eliminating reactive oxygen species (ROS), inhibiting the formation of malondialdehyde (MDA) and promoting to accumulate proline under cold stress. Together, these findings provided insights into the function of RsGRAS genes in taproot development and chilling stress response in radish. • The GRAS gene family was comprehensively characterized in radish. • Expression analysis indicates RsSHRc might be involved in radish taproot thickening. • Transient expression analysis revealed RsSHRc gene could enhance cold tolerance of radish plants. [ABSTRACT FROM AUTHOR]