The main mission of the Center for Molecular Agrobiology (CMA) is to conduct genetic and breeding research in the major crops, with emphases on studying the molecular mechanisms underlying agronomic traits and the development of new crop varieties. In 2016, CMA scientists have made a series of important progresses in the research on genetic control of complex agronomic traits,genome editing techniques,the improvement of nutrient use efficiency and molecular mechanisms of pathogen resistance, etc.

 

Genetic Architecture of Complex Agronomic Traits: Yunhai Li’s Group revealed that the F-box protein SAP controls meristemoid cell proliferation and organ size by targeting PPD proteins for degradation (Wang et al., Nat Commun, 2016). They showed that DA3 controls seed and organ size by regulating the stability of cyclin (CYCA2;3) and cyclin-dependent kinase (CDKB1;1) (Xu et al., Plant Cell, 2016). In addition, they defined a regulatory mechanism of the miR396-GS2/OsGRF4-OsGIFs module in grain size control (Duan et al., Nat Plants, 2016). Using 809 diverse soybean accessions worldwide and genome-wide association studies, Zhixi Tian’s group identified 245 significant genetic loci and network analyses demonstrated that some associated loci exhibited pleiotropy, whereas others were linked on short fragments. This study provides insights into the genetic correlation among complex traits and will facilitate future soybean functional studies and breeding by molecular design. Cuimin Liu’s Group successfully resolved the structure of GPI, a key enzyme in starch metabolic pathways in wheat. They found two amino acid residues can significantly improve the activity of GPI, while one residue can severely reduce its activity. It will insight into the studies of biochemical properties, protein structures and regulation networks of GPI, and also provides new strategies of breeding wheat for grain quality.

 

Molecular Mechanisms of Pathogen Resistance: Qianhua Shen’s group identified an E3 ubiquitin ligase which was interact with several barley MLA immune receptors against powdery mildew fungus, and revealed a mechanism for stability control of immune receptors and for the attenuation of defense signaling via the ubiquitin proteasome system (Wang et al., Plant Physiol, 2016). Zhiyong Liu’s group identified and constructed fine genetic linkage map and physical map of wheat spot blotch resistance gene Sb3, providing a framework for map-based cloning of Sb3 and marker-assisted selection (MAS) of spot blotch resistance in wheat breeding programs (Lu et al., Theor Appl Genet, 2016). Daowen Wang’s group found the gene co-expression networks (GCN) and regulation mechanism, the major modules and the hub genes of the powdery mildew resistance regulated genes in immune (IM) and hypersensitive reaction (HR) resistance responses. These findings provide a new insight into the molecular mechanism in wheat resistance to Blumeria graminis f.sp. tritici (Bgt) (Zhang et al., Sci Rep, 2016). Dingzhong Tang’s group showed that an Arabidopsis mutant cyp83a1-3 exhibited enhanced defense responses to the powdery mildew fungus Golovinomyces cichoracearum. The CYP83A1A gene encods cytochrome P450 83A1 monooxygenase, which functions in glucosinolate biosynthesis. Decreasing camalexin levels by mutation of the camalexin synthetase gene PAD3 or the camalexin synthesis regulator AtWRKY33 compromised the powdery mildew resistance. These results indicated that CYP83A1 may regulate the accumulation of camalexin through WARK33 to modulate powdery mildew resistance(Liu et al., Front Plant Sci, 2016).

 

The Improvement of Nutrient Use Efficiency: Yiping Tong’s group generated a wheat plant of knocking out TaPHO2-A1 significantly increased phosphorus uptake and grain yield under low phosphorus conditions. It provides useful cue to improve wheat yield with less phosphorus fertilizer input through engineering PHO2 expression level by genome editing approach (Ouyang et al., Sci Rep. 2016). Hongqing Ling’s group analyzed the molecular characterization of the AtSPX3 promoter, and demonstrated that both P1BS (AtPHR1 binding site) and AtMyb4 (MYB4 putative binding site) elements were two main cis-elements in the AtSPX3 promoter. They found that AtPHR1, a key transcription factor in Pi homeostasis of plant, was required for the negative regulation function of AtMyb4 element in shoots (Li et al., Plant Cell Physiol, 2016). Xiangdong Fu’s group found that Arabidopsis ELONGATED HYPOCOTYL5 (HY5), a bZIP transcription factor that regulates plant growth in response to light, is a shoot-to-root mobile signal that coordinates light-responsive carbon and nitrogen metabolism, and hence shoot and root growth, in a whole-organismal response to ambient light fluctuations. The finding enhances understanding of how plant C and N nutrient balance is maintained in fluctuating environments and suggests novel strategies for the improvement of nutrient-use efficiency in crops (Chen et al., Curr Biol, 2016).

 

Genome Editing Techniques: Caixia Gao’s group developed the efficient intron-mediated site-specific gene replacement and insertion approaches using the CRISPR-Cas9 system, which generate mutations using the nonhomologous end joining (NHEJ) pathway (Li et al., Nat Plants, 2016). They also developed an efficient and transgene-free genome editing in wheat through transient expression of CRISPR/Cas9 DNA or RNA (Zhang et al., Nat Commun, 2016).

 

Plant Chromosome Engineering: Zhensheng Li’s group developed a translocation line Xiaoyan 447 and an addition line Xiaoyan85 derived from the crosses between Th. ponticum, wheat-Th. ponticum partial amphiploids and wheat, respectively. Both Xiaoyan 447 and Xiaoyan 85 display acceptable resistance to Ug99 races at seedling and adult stages (Li et al., J Genet Genomics, 2016). Fangpu Han's group investigated two maize de novo centromeres atypically located in euchromatin, and found that seeding of CENH3, the centromere-specific histone, was affected by intrinsic DNA methylation patterns before neocentromere formation and that CENH3 loading can also shape the DNA methylation patterns after de novo centromere formation (Su et al., Plant J, 2016). In addition, Huabang Chen's group performed map-based cloning and abortion mechanism analysis of maize ABNORMAL POLLEN ACUOLATION GENE 1 (APV1). Aimin Zhang's group carried on genome-wide QTL mapping and gain further knowledge on genetic architecture of grain size in einkorn wheat. Xiangqi Zhang's group identified several new high-molecular-weight glutenin subunit genes from Roegneria nakaii and R. alashanica, and investigated their structural characteristics and phylogenetic relationships. These studies provide new clues and resources for dissection of complex agronomic traits.

 

Breeding of New Varieties: Zhiyong Liu’s group developed new wheat lines for National Yellow & Huai Rivers Regional Test and Henan Provincial Regional Test in 2016. Baoge Zhu’s group created several the special nutrient soybean germplasms and bred excellent lines by molecular breeding system, and twelve breeding lines were participated the National Regional Test or Provincial Regional Test in 2016.