Abstract
To identify genes associated with genic male sterility (GMS) that could be useful for hybrid breeding in Chinese cabbage ( Brassica rapa ssp. pekinensis ), floral bud transcriptome analysis was carried out using a B . rapa microarray with 300,000 probes (Br300K). Among 47,548 clones deposited on a Br300K microarray with seven probes of 60 nt length within the 3' 150 bp region, a total of 10,622 genes were differentially expressed between fertile and sterile floral buds; 4,774 and 5,848 genes were up-regulated over 2-fold in fertile and sterile buds, respectively. However, the expression of 1,413 and 199 genes showed fertile and sterile bud-specific features, respectively. Genes expressed specifically in fertile buds, possibly GMS-related genes, included homologs of several Arabidopsis male sterility-related genes, genes associated with the cell wall and synthesis of its surface proteins, pollen wall and coat components, signaling components, and nutrient supplies. However, most early genes for pollen development, genes for primexine and callose formation, and genes for pollen maturation and anther dehiscence showed no difference in expression between fertile and sterile buds. Some of the known genes associated with Arabidopsis pollen development showed similar expression patterns to those seen in this study, while others did not. BrbHLH89 and BrMYP99 are putative GMS genes. Additionally, 17 novel genes identified only in B . rapa were specifically and highly expressed only in fertile buds, implying the possible involvement in male fertility. All data suggest that Chinese cabbage GMS might be controlled by genes acting in post-meiotic tapetal development that are different from those known to be associated with Arabidopsis male sterility.
Highlights
Pollen development, a process stemming from anther cell division and differentiation leading to male meiosis, as well as pollen wall and coat development and anther dehiscence, relies on the functions of numerous genes from both the microspore itself and sporophytic anther tissues including the tapetum [1,2,3,4,5,6,7]
Using a B. rapa-specific microarray, transcriptome analysis from floral buds, which include both gametophytic and sporophytic tissues, was conducted to identify genes associated with genic male sterility (GMS) in Chinese cabbage
Tapetal function and pollen development are controlled by several transcription factor genes in a sequential and overlapping manner. These include: DYT1 (DYSFUNCTIONAL TAPETUM1), controlling an early tapetal developmental stage [35]; TDF1 (Tapetal Development and Function 1), controlling callose dissolution around microspores and exine formation of the pollen wall [36]; and AMS (ABORTED MICROSPORES), MS1 (MALE STERILITY 1), and MYB103/80, controlling post-meiotic tapetal function and pollen development [28,35]
Summary
A process stemming from anther cell division and differentiation leading to male meiosis, as well as pollen wall and coat development and anther dehiscence, relies on the functions of numerous genes from both the microspore itself and sporophytic anther tissues including the tapetum [1,2,3,4,5,6,7]. Using a B. rapa-specific microarray, transcriptome analysis from floral buds, which include both gametophytic and sporophytic tissues, was conducted to identify genes associated with genic male sterility (GMS) in Chinese cabbage. Tapetal function and pollen development are controlled by several transcription factor genes in a sequential and overlapping manner These include: DYT1 (DYSFUNCTIONAL TAPETUM1), controlling an early tapetal developmental stage [35]; TDF1 (Tapetal Development and Function 1), controlling callose dissolution around microspores and exine formation of the pollen wall [36]; and AMS (ABORTED MICROSPORES), MS1 (MALE STERILITY 1), and MYB103/80, controlling post-meiotic tapetal function and pollen development [28,35]. All data analyzed in this study indicated that Chinese cabbage GMS might be controlled by genes acting in post-meiotic tapetal development
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