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CLAVATA3/EMBRYO SURROUNDING REGION-related (CLE) peptides are a class of small molecules involved in plant growth and development. Although radish (Raphanus sativus) is an important root vegetable crop worldwide, the functions of CLE peptides in its taproot formation remain elusive. Here, a total of 48 RsCLE genes were identified from the radish genome. RNA in situ hybridization showed that RsCLE22a gene was highly expressed in the vascular cambium. Overexpression of RsCLE22a inhibited root growth by impairing stem cell proliferation in Arabidopsis, and radish plants with exogenous supplementation of RsCLE22 peptide (CLE22p) showed a similar phenotype. The vascular cambial activity was increased in RsCLE22a -silenced plants. Transcriptome analysis revealed that CLE22p altered the expression of several genes involved in meristem development and hormone signal transduction in radish. Immunolocalization results showed that CLE22p increased auxin accumulation in vascular cambium. Yeast one-hybrid and dual-luciferase assays showed that the WUSCHEL-RELATED HOMEOBOX 4 (RsWOX4) binds to RsCLE22a promoter and activates its transcription. The expression level of RsWOX4 was related to vascular cambial activity and was regulated by auxin. Furthermore, a RsCLE22a–RsWOX4 module is proposed to regulate taproot vascular cambium activity through an auxin signaling-related pathway in radish. These findings provide novel insights into the regulation of root growth in a horticultural crop. [ABSTRACT FROM AUTHOR]

Background: Taproot is the main edible organ and ultimately determines radish yield and quality. However, the precise molecular mechanism underlying taproot thickening awaits further investigation in radish. Here, RNA-seq was performed to identify critical genes involved in radish taproot thickening from three advanced inbred lines with different root size. Results: A total of 2606 differentially expressed genes (DEGs) were shared between 'NAU-DY' (large acicular) and 'NAU-YB' (medium obovate), which were significantly enriched in 'phenylpropanoid biosynthesis', 'glucosinolate biosynthesis', and 'starch and sucrose metabolism' pathway. Meanwhile, a total of 16 differentially expressed miRNAs (DEMs) were shared between 'NAU-DY' and 'NAU-YH' (small circular), whereas 12 miRNAs exhibited specific differential expression in 'NAU-DY'. Association analysis indicated that miR393a-bHLH77, miR167c-ARF8, and miR5658-APL might be key factors to biological phenomenon of taproot type variation, and a putative regulatory model of taproot thickening and development was proposed. Furthermore, several critical genes including SUS1, EXPB3, and CDC5 were characterized and profiled by RT-qPCR analysis. Conclusion: This integrated study on the transcriptional and post-transcriptional profiles could provide new insights into comprehensive understanding of the molecular regulatory mechanism underlying taproot thickening in root vegetable crops. [ABSTRACT FROM AUTHOR]

Radish (Raphanus sativus L.) is an economically important and widely cultivated root vegetable crop. The coloration of the green skin and green flesh is an important trait influencing the nutrition and flavor quality in fruit radish. GOLDEN2-LIKEs (GLKs) play critically important roles in plastid development and chlorophyll biosynthesis in plants. However, the molecular mechanism underlying chlorophyll biosynthesis still remain elusive in green fruit radish taproot. Herein, the RsGLK2.1 gene exhibited higher expression level in taproot with a green skin (GS) and green flesh (GF) than that in taproot of the white or red radish genotypes. RsGLK2.1 is a nuclear transcription factor that has intrinsic transcriptional activation activity. Overexpression of RsGLK2.1 increased the total chlorophyll content of 20.68%–45.84% in radish leaves. Knockout of the RsGLK2.1 gene via CRISPR/Cas9 technology resulted in a significant decrease in the chlorophyll content. Overexpression of the RsGLK2.1 gene could restore the phenotype of the glk1glk2 mutant Arabidopsis. RsGLK2.1 was participated in regulating the chlorophyll biosynthesis by directly binding to the promoter of RsHEMA2 and activating its transcription. The interaction of RsNF-YA9a with RsGLK2.1 increased the transcriptional activity of the downstream gene RsHEMA2 under the light condition rather than the dark condition, indicating that both of them regulate the chlorophyll biosynthesis in a light-dependent manner of radish. Overall, these results provided insights into the molecular framework of the RsGLK2.1-RsNF-YA9a module, and could facilitate dissecting the regulatory mechanism underlying chlorophyll biosynthesis in green taproot of radish, and genetic improvement of quality traits in fruit radish breeding programs. • RsGLK2.1 exhibits higher expression level in green taproot than that in white and red radish. • Overexpression of RsGLK2.1 increased the total chlorophyll content in radish leaves. • Knock-down and knock-out of the RsGLK2.1 decreased the chlorophyll content in radish. • The interaction of RsNF-YA9a with RsGLK2.1 positively regulated chlorophyll biosynthesis. [ABSTRACT FROM AUTHOR]

Radish is an economical cool-season root vegetable crop worldwide. Heat shock protein 70 (HSP70) plays indispensable roles in plant growth, development and abiotic stress responses. Nevertheless, little information is available regarding the identification and functional characterization of HSP70 gene family in radish. Herein, a total of 34 RsHSP70 genes were identified at the radish genome level, among which nine and 25 RsHSP70s were classified into the HSP110/SSE and DnaK subfamilies, respectively. RNA-seq analysis revealed that some RsHSP70 genes had differential expression profile in radish leaf, root, stamen and pistil. A range of RsHSP70 genes exhibited differential expression under several abiotic stresses such as heat, salt and heavy metals. Intriguingly, the expression of four RsHSP70 genes (RsHSP70-7 , RsHSP70-12 , RsHSP70-20 and RsHSP70-22) was dramatically up-regulated under heat stress (HS). RT-qPCR and transient LUC reporter assay indicated that both the expression and promoter activity of RsHSP70-20 was strongly induced by HS. Notably, overexpression of RsHSP70-20 significantly enhanced thermotolerance by decreasing reactive oxygen species and promoting proline accumulation in radish, whereas its knock-down plants exhibited increased thermosensitivity, indicating that RsHSP70-20 positively regulate HS response in radish. These results would provide valuable information to decipher the molecular basis of RsHSP70 -mediated thermotolerance in radish. [Display omitted] • RsHSP70 gene family was systematically characterized at genome-wide level in radish. • Expression and promoter activity of RsHSP70-20 was markedly induced by heat stress. • Transgenic analysis reveals that RsHSP70-20 enhanced thermotolerance of radish plant. [ABSTRACT FROM AUTHOR]