Small auxin upregulated RNA (SAUR) gene family in maize: identification, evolution, and its phylogenetic comparison with Arabidopsis, rice, and sorghum.

Small auxin-up RNAs (SAURs) are the early auxin-responsive genes represented by a large multigene family in plants. Here, we identified 79 SAUR gene family members from maize (Zea mays subsp. mays) by a reiterative database search and manual annotation. Phylogenetic analysis indicated that the SAUR proteins from Arabidopsis, rice, sorghum, and maize had divided into 16 groups. These genes were non-randomly distributed across the maize chromosomes, and segmental duplication and tandem duplication contributed to the expansion of the maize SAUR gene family. Synteny analysis established orthology relationships and functional linkages between SAUR genes in maize and sorghum genomes. We also found that the auxin-responsive elements were conserved in the upstream sequences of maize SAUR members. Selection analyses identified some significant site-specific constraints acted on most SAUR paralogs. Expression profiles based on microarray data have provided insights into the possible functional divergence among members of the SAUR gene family. Quantitative real-time PCR analysis indicated that some of the 10 randomly selected ZmSAUR genes could be induced at least in maize shoot or root tissue tested. The results reveal a comprehensive overview of the maize SAUR gene family and may pave the way for deciphering their function during plant development.

Chen Y ，Hao X ，Cao J 《-》

Genome-wide analysis, evolutionary expansion, and expression of early auxin-responsive SAUR gene family in rice (Oryza sativa).

Small auxin-up RNAs (SAURs) are the early auxin-responsive genes represented by a large multigene family in plants. Here, we report the identification of 58 OsSAUR gene family members from rice (Oryza sativa japonica cv Nipponbare), the model monocot plant, by a reiterative database search and manual reannotation; 2 of these are pseudogenes. The coding sequences of OsSAURs do not possess any intron. Most of the predicted OsSAUR protein sequences harbor a putative nuclear localization signal at their N-terminus. Localized gene duplications appear to be the primary genetic event responsible for SAUR gene family expansion in rice. Interestingly, the duplication of OsSAURs was found to be associated with the chromosomal block duplication as well. The phylogenetic analysis revealed that the SAUR gene family expanded in rice and Arabidopsis due to species-specific expansion of the family in monocots and dicots. The auxin-responsive elements and downstream element are conserved in the upstream and downstream sequences, respectively, of OsSAURs. In addition to the 21 OsSAURs with full-length cDNA sequences and 20 with expressed sequence tags, gene expression analyses of at least 7 OsSAURs by RT-qPCR indicated that the majority of identified OsSAURs most likely are expressed in rice. The transcript abundance of the OsSAURs examined increased within a few minutes of exogenous auxin application with varying kinetics. The present study provides basic genomic information for the rice SAUR gene family and will pave the way for deciphering the precise role of SAURs in plant growth and development.

Jain M ，Tyagi AK ，Khurana JP 《GENOMICS》

Genome-wide analysis of WOX gene family in rice, sorghum, maize, Arabidopsis and poplar.

WUSCHEL-related homeobox (WOX) genes form a large gene family specifically expressed in plants. They are known to play important roles in regulating the development of plant tissues and organs by determining cell fate. Recent available whole genome sequences allow us to do more comprehensive phylogenetic analysis of the WOX genes in plants. In the present study, we identified 11 and 21 WOXs from sorghum (Sorghum bicolor) and maize (Zea mays), respectively. The 72 WOX genes from rice (Oryza sativa), sorghum, maize, Arabidopsis (Arabidopsis thaliana) and poplar (Populus trichocarpa) were grouped into three well supported clades with nine subgroups according to the amino acid sequences of their homodomains. Their phylogenetic relationship was also supported by the observation of the motifs outside the homodomain. We observed the variation of duplication events among the nine sub-groups between monocots and eudicots, for instance, more gene duplication events of WOXs within subgroup A for monocots, while, less for dicots in this subgroup. Furthermore, we observed the conserved intron/exon structural patterns of WOX genes in rice, sorghum and Arabidopsis. In addition, WUS (Wuschel)-box and EAR (the ERF-associated amphiphilic repression)-like motif were observed to be conserved among several WOX subgroups in these five plants. Comparative analysis of expression patterns of WOX genes in rice and Arabidopsis suggest that the WOX genes play conserved and various roles in plants. This work provides insights into the evolution of the WOX gene family and is useful for future research.

Zhang X ，Zong J ，Liu J ，Yin J ，Zhang D ... -  《-》

Comparative genomic analysis of the Sm gene family in rice and maize.

Sm proteins are a group of ubiquitous ring-shaped oligomers that function in multiple aspects of RNA metabolism. However, until this study, no comprehensive study incorporating phylogeny, chromosomal location, gene organization, adaptive evolution, expression profiling and functional networks has been reported for rice and maize. In this study, twenty-five and thirty-three Sm genes have been identified in rice and maize, respectively. Phylogenetic analyses identified eighteen gene groups. Results by gene locations indicated that segmental duplication contributes to the expansion of this gene family in rice and maize. Gene organization and motif compositions of the Sm members are highly conserved in each group, indicative of their functional conservation. Expression profiles have provided insights into the possible functional divergence among members of the Sm gene family. Adaptive evolution analyses suggested that purifying selection was the main force driving Sm evolution, but some critical sites might be responsible for functional divergence. In addition, four hundred and seventy-nine interactions were identified by functional network analyses, and most of which were associated with binding, cellular macromolecule biosynthesis, pre-mRNA processing and transferase activity. Overall, the data contribute to a better understanding of the complexity of Sm gene family in rice and maize and will provide a solid foundation for future functional studies.

Chen Y ，Cao J 《-》

A genome-wide analysis of the ERF gene family in sorghum.

Yan HW ，Hong L ，Zhou YQ ，Jiang HY ，Zhu SW ，Fan J ，Cheng BJ ... -  《Genetics and Molecular Research》