Anther and pollen development in barley

The control of pollen viability and release is of major commercial importance in the development of crops for hybrid seed production and selective breeding. It has been shown that key transcription factors in Arabidopsis particularly MALE STERILITY1 (MS1), are functionally conserved in rice (Li et al., 2011), therefore extending this comparative analysis and controlling fertility in temperate cereals, such as barley, is the long term goal of this project. Although anther and pollen development of barley seems morphologically similar to Arabidopsis, the genes involved and how they are regulated are currently unknown. Arabidopsis MS1 is a tapetum specific transcription factor which is expressed exclusively from the tetrad stage to early microspores release. Identification and accurate staging of barley anther development is essential for expression analysis and functional characterisation of genes involved in pollen development. Therefore, a complete morphological study of barley development was conducted. External characteristics have been described in parallel to anther development in order to predict anther stages by the observation of external stages phenotypic traits. Characterization of the barley orthologue of MS1 (HvMS1) has been conducted. Recently a new grass genome has been released, Brachypodium distachyion. This new resource has been used to aid primers design alongside the rice OsPTC1 sequence, the orthologue of MS1 (Li et al., 2011). Genome sequencing has indicated that the Brachypodium genus is more closely related to wheat and barley than it is to rice, Due to the close relationship between Brachypodium and barley, this new grass has been used as intermediary to identify the OsPTC1 orthologue in barley as well as downstream MS1 targets. A highly similar sequence to OsPTC1 was found in Brachypodium, Bradi4g31760. This new gene, as a result of its similarities to OsPTC1, was considered as its putative orthologue gene in Brachypodium. Therefore, the most conserved areas between OsPTC1-Bradi4g31760 were used for primers design to successfully amplify equivalent gene in barley (HvMS1). The characterization of this barley gene showed a similar expression pattern to the MS1 putative orthologue in Arabidopsis of tapetum specific expression. In addition, RNAi silencing of this gene has revealed that it is essential for the normal development of pollen, with a lack of viable pollen produced in the putative HvMS1 silenced transgenic lines