| Wheat (Triticum aestivum L.) is one of the most important crops in the world and provides mostcalories consumed by human beings. We studied two important agronomic trait genes in wheat:TaqSH1and TaDEP1which are associated with seed shattering and thousand grain weight.Seed shattering is one of the major domestication traits of crops. In wheat, except for the Q genewhose mutation renders free threshing and changing of rachis fragility, not much is known about themolecular mechanism for this process. We report here the cloning and characterization of TaqSH1, theortholog of the rice seed shattering gene qSH1. TaqSH1encodes a BEL1-like protein that is conservedamong monocots and eudicots. TaqSH1is located on the homoeologous group3, a potential new geneticlocus for seed threshability in wheat. Over expression of TaqSH1in Arabidopsis resulted in dwarfedplants. The inflorescences of transgenic plants were more compact with larger pedicel angles. ScanningElectron Microscopy showed that the transgenic siliques had narrower replums with altered dehiscencezones. In addition, petal abscission was significantly delayed due to the slow down of abscission zonecell development. Real-time PCR assays showed that over expression of TaqSH1down regulatedseveral known Arabidopsis abscission related genes, such as IDA, HAESA, KNAT1and KNAT6in thetransgenic plants. Taken together, our data suggest that TaqSH1may represent another example ofconserved mechanisms across monocots and eudicots for fruit/grain abscission and should havepotential application in genetic manipulation of wheat seed shattering.The second gene was related to rice DEP1(DENSE AND ERECT PANICLE1) gene. DEP1was amajor quantitative trait loci (QTLs) that controlled grain yield. There are truncated deletions in theC-terminal of the mutant DEP1allele (dep1). Dep1is an important regulator that can enhance meristemactivity, reduce inter-node distance, increase per spike grain number, and eventually increase the riceyield. We report here further characterization of the DEP1gene (TaDEP1) in wheat. Chromosomalmapping showed that TaDEP1was located on chromosomes of homoeologous group5. An InDelmarker was developed from its first intron and was mapped to chromosome5B. This marker (tentativelynamed dep1-5b) was used to fine map TaDEP1into a~10cM region between genetic markers GS34and S67on the5B long arm. We then genotyped262wheat accessions from the wheat core germplasmcollection (CWGC) using dep1-5b. Association analysis revealed that dep1-5b was significantlyassociated with higher one-thousand grain weight (TGW) in the two year dataset among CWGC. Whenwe divided the CWGC accessions into subpopulations of landraces and cultivars, we found that dep1-5bwas significantly associated with grain yield only in the landraces but not in the cultivars. Two kinds ofalleles are found in rice with the dep1alleles contributing to grain yield increase. We observed the genestructures in other grasses, and found that shorter/truncated alleles were present in nearly all grassspecies surveyed, including the progenitors of bread wheat (T. uratu, Ae. tauschii, and T. turgidum),Brachypodium and sorghum contrasting to the existence of both long and short alleles in rice.Interestingly, we found two alleles (long and short) respectively located in chromosome2and7ofmaize. The observation was consistent with association analysis result. Shorter allele in most of the grass species was reserved by domestication and longer allele lost; TaDEP1was significantly associatedwith TGW in the CWGC but not in the cultivars of artificial selection. It indicated that theshorter/truncated allele was possibly a domesticated gene. |
