Hao Zhou

Allopolyploidization has been a driving force in plant evolution. Formation of common wheat (Triticum aestivum L.) represents a classic example of successful speciation via allopolyploidy. Nevertheless, the immediate chromosomal consequences of allopolyploidization in wheat remain largely unexplored. We report here an in-depth investigation on transgenerational chromosomal variation in resynthesized allohexaploid wheats that are identical in genome constitution to common wheat. We deployed sequential FISH, genomic in situ hybridization (GISH), and homeolog-specific pyrosequencing, which enabled unequivocal identification of each of the 21 homologous chromosome pairs in each of >1,000 individual plants from 16 independent lines. We report that whole-chromosome aneuploidy occurred ubiquitously in early generations (from selfed generation S(1) to >S(20)) of wheat allohexaploidy although at highly variable frequencies (20-100%). In contrast, other types of gross structural variations were scant. Aneuploidy included an unexpected hidden type, which had a euploid chromosome number of 2n = 42 but with simultaneous loss and gain of nonhomeologous chromosomes. Of the three constituent subgenomes, B showed the most lability for aneuploidy, followed by A, but the recently added D subgenome was largely stable in most of the studied lines. Chromosome loss and gain were also unequal across the 21 homologous chromosome pairs. Pedigree analysis showed no evidence for progressive karyotype stabilization even with multigenerational selection for euploidy. Profiling of two traits directly related to reproductive fitness showed that although pollen viability was generally reduced by aneuploidy, the adverse effect of aneuploidy on seed-set is dependent on both aneuploidy type and synthetic line.

Subgenome integrity in bread wheat (Triticum aestivum; BBAADD) makes possible the extraction of its BBAA component to restitute a novel plant type. The availability of such a ploidy-reversed wheat (extracted tetraploid wheat [ETW]) provides a unique opportunity to address whether and to what extent the BBAA component of bread wheat has been modified in phenotype, karyotype, and gene expression during its evolutionary history at the allohexaploid level. We report here that ETW was anomalous in multiple phenotypic traits but maintained a stable karyotype. Microarray-based transcriptome profiling identified a large number of differentially expressed genes between ETW and natural tetraploid wheat (Triticum turgidum), and the ETW-downregulated genes were enriched for distinct Gene Ontology categories. Quantitative RT-PCR analysis showed that gene expression differences between ETW and a set of diverse durum wheat (T. turgidum subsp durum) cultivars were distinct from those characterizing tetraploid cultivars per se. Pyrosequencing revealed that the expression alterations may occur to either only one or both of the B and A homoeolog transcripts in ETW. A majority of the genes showed additive expression in a resynthesized allohexaploid wheat. Analysis of a synthetic allohexaploid wheat and diverse bread wheat cultivars revealed the rapid occurrence of expression changes to the BBAA subgenomes subsequent to allohexaploidization and their evolutionary persistence.

In the present study, nine endophytic strains of Diaporthe from China were identified based on analyses of morphological characters and combined sequences of rDNA ITS, partial sequences from the translation elongation factor 1-α (tef1), β tubulin (tub2), histone H3 (his3), and calmodulin (cal) genes. Three new Diaporthe species, Diaporthe anhuiensis, Diaporthe huangshanensis and Diaporthe shennongjiaensis, are introduced in this paper with full descriptions and comparison with similar taxa. And two other known species, Diaporthe citrichinensis and Diaporthe eres are also described.

Zokors in the genus <i>Eospalax</i>, which are endemic to northern and western China, are subterranean rodents that inhabit various niches, including grasslands, high-altitude meadows, forests, and farmlands. Six species in <i>Eospalax</i> were described a century ago but their taxonomy and phylogeny remain controversial. In this study, we performed high-depth whole-genome sequencing of 47 zokor samples, comprising all six previously described species. Genomic analyses revealed a reliable and robust phylogeny of <i>Eospalax</i> and supported the validity of the six named species. According to the inferred phylogenetic relationships, <i>Eospalax</i> first divergent into two clades in the early Pliocene (ca. 4.68 million years ago (Ma)), one inhabiting the high-altitude Qinghai-Xizang (Tibet) Plateau (QTP) and adjacent regions, and the another inhabiting the low-altitude Loess Plateau and Qinling-Daba Mountains. The most recent divergences occurred between <i>E. baileyi</i> and <i>E. smithii</i> and between <i>E. rufescens</i> and <i>E. rothschildi</i> in the late Pliocene (ca. 2.09 and 2.19 Ma, respectively). We also collected specimens of zokors in the southern Hengduan Mountains (Muli County, Sichuan Province), far from the known distributions of all other zokors. Morphological and molecular analyses strongly suggested that the specimens represent a new species, formally described here as <i>Eospalax muliensis</i> <b>sp. nov</b> . The new species belongs to the high-altitude clade and diverged from closely related species (ca. 4.22 Ma) shortly after the first divergence in <i>Eospalax</i>. Interestingly,<i> Eospalax muliensis</i> <b>sp. nov</b> . possesses more supposedly plesiomorphic characters, suggesting a possible origin of the genus in the Hengduan Mountains.

Three new species, Candolleomyces incanus , C. subcandolleanus and C. yanshanensis , were found and described from Yanshan Mountains in China. The identification is based on morphological observation combined with phylogenetic analysis of ITS-LSU- Tef1α - TUB2 . This study enriched the species diversity of Candolleomyces in Yanshan Mountains and provided important data support for the systematic study of Candolleomyces in the future.