*2.2. The Number of EXO70s in Genomes of Triticeae Species*

The diploid species *B. distachyon* and *Arabidopsis* have 22 and 23 *EXO70s*, respectively, while diploid rice has 41, nearly twice as many. We identified 22 *EXO70s* each in A and D of common wheat and B of the tetraploid wheat, 25 in A of tetraploid wheat, 26 in D of *Ae. Tauschii* and H of barley and 29 *EXO70s* in B of common wheat. For the A genome, tetraploid has three more *EXO70s* than hexaploidy wheat; for the B genome, hexaploidy has seven more than tetraploid wheat; for the D genome, *Ae. tauschii* has four more *EXO70s* than hexaploidy wheat. In common wheat, the chromosomes 5A, 5B and 5D had the same number of *EXO70s*, belonging to the same gene type and having the same gene order. The chromosomes 7A, 7B and 7D also have the same number of *EXO70s*; however, their gene type and gene order were not completely the same. For example, *TaEXO70D* is only present on 7A and 7B, but not on 7D; *TaEXO70G1* is only present on 7A and 7D, but not 7B. The gene number and order for *EXO70s* in the remaining five homoeologous were also different among corresponding homoeologous chromosomes, mainly due to their difference for subgroup *EXO70I* (Tables 2 and S2).


**\*** The genes that were assigned to unknown chromosome.

The three analyzed diploid *Triticea* species, *H. vulgare*, *T. uratu* and *Ae. tauschii*, each had 26 *EXO70s* and had the same number as the *EXO70B*, *C*, *D* and H subgroups. They had the least *EXO70Hs* and the most *EXO70Is*. *T. uratu* only had one *EXO70G*, while the other two species had three. However, *T. uratu* had more *EXO70I* than the other two species (Table 3). The variation among different diploid species may be due either to the quality of the genome assembly or the duplication or deletion during evolution. The tetraploid *T. dicoccoides* and hexaploid *T. aestivum* have 47 and 75 *EXO70s*, which are about twice and three times the number in diploid species, respectively. In addition, the number of *EXO70s* from each subgroup is also exactly (*EXO70C*, *H*) or almost (*EXO70A*, *B*, *D*, *E*, *F*, *I*) 2 or 3 times that of the diploid species (Table 3). This indicated that, in polyploid wheat, the increased number of *EXO70s* is mostly due to the genome polyploidization.

We only identified 15 *EXO70s* in diploid *H. villosa*, which is much less than the average number for other diploid species. *H. villosa* had the same number of subgroups D and H, but fewer members of subgroups B, C, E, F and I. This is due either to the lack of the sequence of *H. villosa*, or the divergence of *H. villosa* from other *Triticea* species (Table 3).


**Table 3.** Numbers of *EXO70* paralogs encoded by the surveyed genomes in total and individual subgroups.

Numbers in brackets indicate number of copies for polyploid genomes.
