In higher plants, male reproductive development is a complex biological process that includes cell division and differentiation, cell to cell communication etc., while the mechanism underlying plant male reproductive development remains less understood. GAMYB encodes a gibberellins acid （GA） inducible transcription factor that is required for the early anther development in rice （Oryza sativa L.）. Here, we report the isolation and characterization of a new allele gamyb-4 with a C base deletion in the second exon （-I-2308）, causing a frame shift and premature translational termination. Histological analysis showed that gamyb-4 developed abnormal enlarged tapetum and could not undergo normal meiosis. To understand the regulatory role of GAMYB, we carried out quantitative reverse transcription-polymerase chain reaction analysis and comparison of microarray data. These results revealed that the expression of TDR （TAPETUM DEGENERATION RETARDATION）, a tapetal cell death regulator, was downregulated in gamyb-4 and udtl （undeveloped tapetuml）. While the GAMYB expression was not obviously changed in tdr and udtl-1, and no apparent expression fold change of UDT1 in tdr and gamyb-4, suggesting that TDR may act downstream of GAMYB and UDT1, and GAMYB and UDT1 work in parallel to regulate rice early anther development. This work is helpful in understanding the regulatory network in rice anther development.
Male reproductive development is a complex biological process which includes the formation of the stamen with differentiated anther tissues, in which microspores/pollens are generated, then anther dehiscence and subsequently pollination. Stamen specification and anther development involve a number of extraordinary events such as meristem transition, cell division and differentiation, cell to cell communication, etc., which need the cooperative interaction of sporophytic and gametophytic genes. The advent of various tools for rice functional gene identification, such as complete genome sequence, genome-wide microarrays, collections of mutants, has greatly facilitated our understanding of mechanisms of rice stamen specification and anther development. Male sterile lines are critical for hybrid rice breeding, therefore understanding these processes will not only contribute greatly to the basic knowledge of crop developmental biology, but also to the development of new varieties for hybrid rice breeding in the future.
WUSCHEL-related homeobox （WOX） genes form a large gene family specifically expressed in plants.They are known to play important roles in regulating the development of plant tissues and organs by determining cell fate.Recent available whole genome sequences allow us to do more comprehensive phylogenetic analysis of the WOX genes in plants.In the present study,we identified 11 and 21 WOXs from sorghum （Sorghum bicolor） and maize （Zea mays）,respectively.The 72 WOX genes from rice （Oryza sativa）,sorghum,maize,Arabidopsis （Arabidopsis thaliana） and poplar （Populus trichocarpa） were grouped into three well supported clades with nine subgroups according to the amino acid sequences of their homodomains.Their phylogenetic relationship was also supported by the observation of the motifs outside the homodomain.We observed the variation of duplication events among the nine sub-groups between monocots and eudicots,for instance,more gene duplication events of WOXs within subgroup A for monocots,while,less for dicots in this subgroup.Furthermore,we observed the conserved intron/exon structural patterns of WOX genes in rice,sorghum and Arabidopsis.In addition,WUS （Wuschel）-box and EAR （the ERF-associated amphiphilic repression）-like motif were observed to be conserved among several WOX subgroups in these five plants.Comparative analysis of expression patterns of WOX genes in rice and Arabidopsis suggest that the WOX genes play conserved and various roles in plants.This work provides insights into the evolution of the WOX gene family and is useful for future research.
Microsporogenesis and male gametogenesis are essential for the alternating life cycle of flowering plants between diploid sporophyte and haploid gametophyte generations. Rice （Oryza sativa） is the world＇s major staple food, and manipulation of pollen fertility is particularly important for the demands to increase rice grain yield. Towards a better understanding of the mechanisms controlling rice male reproductive development, we describe here the cytological changes of anther development through 14 stages, including cell division, differentiation and degeneration of somatic tissues consisting of four concentric cell layers surrounding and supporting reproductive cells as they form mature pollen grains through meiosis and mitosis. Furthermore, we compare the morphological difference of anthers and pollen grains in both monocot rice and eudicot Arabidopsis thaliana. Additionally, we describe the key genes identified to date critical for rice anther development and pollen formation.
