1 INTRODUCTION
Wheat is critical to food security worldwide. Tilletia laevisKühn lead to common bunt, which seriously reduce wheat grain quality and
yield in wheat growing regions of the world (Albughobeish et al., 2015),
the average yield losses by the bunt pathogens can reach 70-80% in some
wheat producing areas (Goates et al., 2012). Additionally, wheat dwarf
bunt caused by Tilletia controversa Kühn , the teliospores or
bunt sori of the T. controversa can last for 10 years in soil and
are easily dispersed from field to field with soil, or can blowout to
new places by infected wheat seeds (Gao et al., 2014). The bunt sori
have a strong odor like of rotting fish, which heavily degrade the
quality of the wheat seeds and flour (Gaudet et al., 2007). Even
slightly low infection can result in clear smell in flour minced from
infected grains (Chen et al., 2016; Nguyen et al., 2019). Also, T.
controversa is an internationally important quarantine pathogen and
many countries have strict restriction on importing wheat from areas
where the disease occurs (Mathre et al., 1996; Gao et al., 2014). Both
pathogens grow vigorously and disrupt the normal structure of wheat
anther (JIA et al., 2013; Bokore et al., 2019), which can infect
reproductive organs at different stages of anther development causing
some of the most economically important plant diseases (Ngugi & Scherm,
2006).
In every anther lobe, cell differentiation and division produce pollen
mother cells (PMC), which are bounded by four somatic layers, epidermis
(EPI), endothecium (EN), middle layer (ML) and tapetum (TA) from the
outside to inside (Scott et al., 2004; Chang et al., 2011; Xu et al.,
2016; Browne et al., 2018). EPI prevent water loss and have role in
dehiscence and in gas exchange, EN and ML have a role in cell structure
and support to the other cells (Goldberg et al., 1993; Sun et al.,
2007). TA plays vital roles in supporting pollen grain development
succeeding the completion of meiosis and meiotic cytokinesis (Zhang et
al., 2006; Browne et al., 2018). Additionally, TA is the innermost layer
of the anthers and have a role to provides the nutrients to the emerging
pollen grain and it undergoes to program cell death in the later stages
of pollen grain development. Microspores (MP) are involved in the pollen
grain and sperm cell development (Zhang & Wilsonc, 2009). Anther is
particularly more sensitive to biotic and abiotic factors (Hedhlyet al.,
2009) during development (Saini & Westgate, 1999; Dolferus et al.,
2011). Ustilago maydis causes disturbance in the anther lobes and
infected organs (Walbot & Skibbe, 2010) which changed the cells of
anther lobes of maize i.e. EPI, EN, SPL, ML and TA, which are involved
in the development of pollen mother cells (Gao et al., 2013).RAFTIN have a role in TA development of cereal crops (Wang et
al., 2003). MYB transcription factors have a role in anther
development in barley and other cereal crops (Murray et al., 2003).TaMYB80 influence the pollen grain development in participating
the program cell death of TA cells (Gao et al., 2013; Millar & Gubler,
2005; Xue, 2005)
High-throughput gene expression analysis using RNA-Seq signifies a very
powerful tool for transcriptomic description of plants during the
interaction of pathogens and plants (Wang et al., 2009; Massart et al.,
2014). The RNA-Seq has been performed in many crops against different
pathogens, such as banana and Fusarium oxysporum f. sp.cubense (Li, 2013), mango and Fusarium mangiferae (Liu et
al., 2016), potato and Phytophthora infestants (Gao et al., 2013)
and so on.
Virus-induced gene silencing (VIGS) has been developed as an effective
genetics tool for assessing gene functions in different plants species
including maize, pea, wheat, tobacco, tomato and barley (Constantin et
al., 2004; Scofield et al., 2005; Ding et al., 2006). Previous studies
revealed functional analysis of wheat genes against Zymoseptoria
tritici resistance and susceptibility (Lee et al., 2015) used forLr21 -mediated leaf rust resistance pathway in hexaploid wheat
(Gao et al., 2013), and established in wheat spikes and grains for
HMW-GS-encoding genes, in which clear photobleaching symptoms were
appeared in silenced plants (Ma et al., 2012).
In this study, we used confocal microscopy to build up the timeline of
wheat anther development, which showed the characteristics of cell types
in wheat anther, and the anther timeline was approved by section and
quantification of anther developmental genes using qRT-PCR assays. In
addition, RNA-Seq was used to analyze wheat anther stages transcriptome
changes in response to T. laevis and T. controversainfection. VIGS was used to silence one of anther development genes in
RNA-Seq to explore the function of anther genes in the infection process
of T. laevis and T. controversa . This is the first report
of the bunt pathogens reprogrammed the anther development based on
confocal microscope and RNA-Seq analysis, and explore related gene’s
function by VIGS technique.