Normal and Abortive Buds Transcriptomic Profiling of Broccoli ogu Cytoplasmic Male Sterile Line and Its Maintainer

Abstract

Bud abortion is the main factor affecting hybrid seeds’ yield during broccoli cross breeding when using ogura cytoplasmic male sterile (ogu CMS) lines. However, the genes associated with bud abortion are poorly understood. We applied RNA sequencing to analyze the transcriptomes of normal and abortive buds of broccoli maintainer and ogu CMS lines. Functional analysis showed that among the 54,753 annotated unigenes obtained, 74 and 21 differentially expressed genes in common were upregulated and downregulated in ogu CMS abortive buds compared with ogu CMS normal buds, maintainer normal, and abortive buds, respectively. Nineteen of the common differentially expressed genes were enriched by GO terms associated with glycosyl hydrolases, reactive oxygen species scavenging, inhibitor, and protein degradation. Ethylene-responsive transcription factor 115 and transcriptional factor basic helix-loop-helix 137 were significantly upregulated; transcription factors DUO1 and PosF21/RF2a/BZIP34 were downregulated in ogu CMS abortive buds compared with the other groups. Genes related to polygalacturonase metabolism, glycosyl hydrolases, oxidation reduction process, phenylalanine metabolism, and phenylpropanoid biosynthesis were significantly changed in ogu CMS abortive buds. Our results increase our understanding of bud abortion, provide a valuable resource for further functional characterization of ogu CMS during bud abortion, and will aid in future cross breeding of Brassica crops.

Differentially expressed genes and phenotypic variation in florets among the isogenic Ogura-CMS, DGMS and inbred lines of broccoli

“…The Ogura-CMS line contributes signi cantly to hybrid seed production in Brassica crops; therefore, some studies focus on Ogura-CMS, although the mechanism of hybrid seed production has not been elucidated. Previous transcriptome and proteome analyses of the Ogura-CMS line have provided basic information about the DEGs and differential abundant proteins (DAPs) between Ogura-CMS lines and their maintainer lines [12,13,17,18,28]. In this study, some signi cant differences in agronomic traits associated with growth and reproductive growth and development were noted among the Ogura-CMS and DGMS lines and their maintainer line in a two-year investigation with statistical analysis.…”

“…Male sterility lines, including Ogura-CMS and DGMS (especially Ogura-CMS), have been widely used in Brassica crops, such as broccoli, cabbage, cauli ower, Chinese cabbage, rape, and radish [7,12,27]. The Ogura-CMS line contributes signi cantly to hybrid seed production in Brassica crops; therefore, some studies focus on Ogura-CMS, although the mechanism of hybrid seed production has not been elucidated.…”

“…The male sterility lines currently used in broccoli breeding were derived from a line with dominant genic male sterility (DGMS), which was discovered in cabbage, and from a line Ogura-CMS, which was discovered in radish [7][8][9][10]. However, there are still some disadvantages regarding bud development and seed production in male sterility lines, especially in Ogura-CMS plants; these disadvantages include bud abortion and low seed yield [7,11,12]. On the other hand, hybrid cultivars from male sterility lines have enhanced seed purity and hybrid rates, and DGMS lines usually have higher seed yields than Ogura-CMS line from the same inbred line [11,13].…”

“…Transcriptome analyses based on RNA sequencing (RNA-Seq) technology are important methods with which to understand the differentially expressed genes (DEGs) involved in various biological processes, and these analyses have been widely performed on Brassica plants [12,13,17,18]. For example, small RNA-Seq has revealed DEGs in the early development of broccoli pollen [19], and transcriptome analyses have been used to examine four transcription factors in normal and abortive buds of an Ogura-CMS line and its maintainer line [12].…”

“…Transcriptome analyses based on RNA sequencing (RNA-Seq) technology are important methods with which to understand the differentially expressed genes (DEGs) involved in various biological processes, and these analyses have been widely performed on Brassica plants [12,13,17,18]. For example, small RNA-Seq has revealed DEGs in the early development of broccoli pollen [19], and transcriptome analyses have been used to examine four transcription factors in normal and abortive buds of an Ogura-CMS line and its maintainer line [12]. In addition, the roles of pigment mechanisms in post-harvest broccoli yellowing [20], gene expression patterns associated with sulforaphane metabolism in broccoli orets [21], glucosinolate metabolism in seeds and sprouts [22,23], and yield heterosis in curds of broccoli have also been elucidated by RNA-Seq technology [24].…”