Comparative cytological and transcriptomic analysis of pollen development in autotetraploid and diploid rice

Abstract

Autotetraploid rice has greater genetic variation and higher vigor than diploid rice, but low pollen fertility is one of the major reasons for low yield of autotetraploid rice. Very little is known about the molecular mechanisms of low pollen fertility of autotetraploid rice. In this study, cytological observations and microarray analysis were used to assess the genetic variation during pollen development in autotetraploid and diploid rice. Many abnormal chromosome behaviors, such as mutivalents, lagged chromosomes, asynchronous cell division, and so on, were found during meiosis in autotetraploid. Microsporogenesis and microgametogenesis in autotetraploid rice was similar to diploid rice, but many different kinds of abnormalities, including microspores degeneration, multi-aperture, and abnormal cell walls, were found in autotetraploid rice. Compared with diploid rice, a total of 1,251 genes were differentially expressed in autotetraploid rice in pollen transcriptome, among them 1,011 and 240 genes were up-regulated and down-regulated, respectively. 124 and 6 genes were co-up-regulated and co-down-regulated during three pollen development stages, respectively. These results suggest that polyploidy induced up-regulation for most of the genes during pollen development. Quantitative RT-PCR was done to validate 12 differentially expressed genes selected from functional categories based on the gene ontology analysis. These stably expressed genes not only related to the pollen development genes, but also involved in cell metabolism, cell physiology, binding, catalytic activity, molecular transducer activity, and transcription regulator activity. The present study suggests that differential expression of some key genes may lead to complex gene regulation and abnormal pollen development in autotetraploid rice.

Polyploidy enhances F1 pollen sterility loci interactions that increase meiosis abnormalities and pollen sterility in autotetraploid rice

“…Similar to normal diploid rice and consistent with descriptions presented in Wu et al, 2014, meiosis in the PMCs of the diploid rice hybrid could be divided into the following nine developmental stages: prophase I, consisting of leptotene, zygotene ( Fig. 2A), pachytene (Fig.…”

“…We previously showed that 125 genes were down-regulated during PMC meiosis in autotetraploid rice (E1-4x) versus diploid rice (E1-2x) and identified one prominent functional gene class with five genes associated with DNAdependent DNA replication (GO: 0006261) in the biological process category. However, we did not identify any significant GO terms in the cellular component category (Wu et al, 2014). In our study, we identified 231 genes that were down-regulated in PMC meiosis of autotetraploid rice (E245-4x) relative to the diploid line (E245-2x) during PMC meiosis (Fig.…”

“…Bright-field microscopy, 4',6-diamidino-2-phenylindole (DAPI) fluorescence staining, and laser capture of individual cells have made it possible to dissect these cells (Fujita et al, 2010;Tang et al, 2010;Yang et al, 2011). Using DAPI fluorescence staining and WE-CLSM techniques, we were able to obtain PMCs at precise stages of meiosis and identify genes that were differentially expressed during these stages in rice (Feng et al, 2001;Lu et al, 2002;Zhang et al, 2005Zhang et al, , 2006He et al, 2011aHe et al, , 2011bWu et al, 2014). Theoretically, the fact that the PSILs have the same genetic background, except at the Sa, Sb, and Sc loci, eliminates the effect of different parental genomes, thus providing insight into the contribution of IE, PE, and IPE but not hybridization of the whole genome on genome-wide expression patterns.…”

“…Our laboratory carried out microarray analysis to assess genetic variation between autotetraploid (Taichung65-4x) and diploid (Taichung65) rice during pollen development. We identified a total of 1,251 differentially expressed genes, some of which are associated with meiosis and pollen development (Wu et al, 2014). Moreover, RNA-seq-based transcriptome profiling revealed that polyploidy is strongly associated with genome-wide disruption of gene expression and ultimately, resulted in aberrant phenotypes in allopolyploid rice hybrids (Xu et al, 2014).…”

Genomic incompatibilities in the diploid and tetraploid offspring of the goldfish × common carp cross

“…These changes may trigger complicated interactions between the repair of DNA damage and the regulation of cell cycles. Another aspect of genome shock maybe also include parentage-biased patterns of gene expression and the abnormal upand down-regulation of offspring genes and abnormality in the very nascent hybrid genomes: e.g., 2nF 1 and 2nF 2 (59,60). We hypothesize that the alteration of expression of these genes drives polyploidization.…”