FLOWERING LOCUS T2 (FT2) is expressed in the distal part of the developing wheat spike and contributes to the regulation of the number of spikelets per spike.
Wheat stripe rust, caused by
Puccinia striiformis
f. sp.
tritici
(
Pst
), is a global threat to wheat production.
Aegilops tauschii
, one of the wheat progenitors, carries the
YrAS2388
locus for resistance to
Pst
on chromosome 4DS. We reveal that
YrAS2388
encodes a typical nucleotide oligomerization domain-like receptor (NLR). The
Pst
-resistant allele
YrAS2388R
has duplicated 3’ untranslated regions and is characterized by alternative splicing in the nucleotide-binding domain. Mutation of the
YrAS2388R
allele disrupts its resistance to
Pst
in synthetic hexaploid wheat; transgenic plants with
YrAS2388R
show resistance to eleven
Pst
races in common wheat and one race of
P
.
striiformis
f. sp.
hordei
in barley. The
YrAS2388R
allele occurs only in
Ae. tauschii
and the
Ae. tauschii
-derived synthetic wheat; it is absent in 100% (
n
= 461) of common wheat lines tested. The cloning of
YrAS2388R
will facilitate breeding for stripe rust resistance in wheat and other Triticeae species.
Salicylic acid (SA) plays an important role in signal transduction and disease resistance. In Arabidopsis, SA can be made by either of two biosynthetic branches, one involving isochorismate synthase (ICS) and the other involving phenylalanine ammonia-lyase (PAL). However, the biosynthetic pathway and the importance of SA remain largely unknown in Triticeae. Here, we cloned one ICS and seven PAL genes from barley, and studied their functions by their overexpression and suppression in that plant. Suppression of the ICS gene significantly delayed plant growth, whereas PAL genes, both overexpressed and suppressed, had no significant effect on plant growth. Similarly, suppression of ICS compromised plant resistance to Fusarium graminearum, whereas similar suppression of PAL genes had no significant effect. We then focused on transgenic plants with ICS. In a leaf-based test with F. graminearum, transgenic plants with an up-regulated ICS were comparable with wild-type control plants. By contrast, transgenic plants with a suppressed ICS lost the ability to accumulate SA during pathogen infection and were also more susceptible to Fusarium than the wild-type controls. This suggests that ICS plays a unique role in SA biosynthesis in barley, which, in turn, confers a basal resistance to F. graminearum by modulating the accumulation of H O , O2- and reactive oxygen-associated enzymatic activities. Although SA mediates systemic acquired resistance (SAR) in dicots, there was no comparable SAR response to F. graminearum in barley. This study expands our knowledge about SA biosynthesis in barley and proves that SA confers basal resistance to fungal pathogens.
Male sterility is a valuable trait for plant breeding and hybrid seed production. The dominant male-sterile gene Ms2 in common wheat has facilitated the release of hundreds of breeding lines and cultivars in China. Here, we describe the map-based cloning of the Ms2 gene and show that Ms2 confers male sterility in wheat, barley and Brachypodium. MS2 appears as an orphan gene within the Triticinae and expression of Ms2 in anthers is associated with insertion of a retroelement into the promoter. The cloning of Ms2 has substantial potential to assemble practical pipelines for recurrent selection and hybrid seed production in wheat.
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