A pinboard by
Ssu-Wei Hsu

Post-doctoral researcher, Academia Sinica


Soybean is the most important crop in the world with a production in 2015 of about 319 million tons of beans. Soybean is also very important for agriculture in the United States because more than 30% of worldwide soybean beans were produced in America. Soybean seed contains high nutritional values and is rich in proteins (with 6-7 fold higher than that of rice and wheat), lipids and carbohydrates which serve as a major source of food for humans. Soybean seed is used to make various foods, such as tofu, soymilk, and soy source. Recently, soybean seed also severs as a promising resource for biofuel due to high lipid content. In the near future, human being will face the challenge of food security and energy crisis because of population explosion. We will need to produce ~70 to 100% more food by 2050. Increased yield may be achieved through modification in developmental traits, e.g., increases in the size, number, and more importantly, nutritional quality of seeds. The aim of my research is to uncover the molecular regulatory mechanism of soybean seed development and help scientists to breed soybean with higher nutritional quality seeds. A complex gene-regulatory networks are involved in soybean seed development. In order to study soybean seed development, various genetic and molecular methods were used in my research. So far, several critical factors (transcription factors) had been identified as the key regulators for biosynthesis of lipids and storage proteins in soybean seed. These factors can be used as genetic and molecular markers for soybean breeding and modification and eventually increase the nutritional value of soybean seeds.


Identification of direct targets of FUSCA3, a key regulator of Arabidopsis seed development.

Abstract: FUSCA3 (FUS3) is a B3 domain transcription factor that is a member of the LEAFY COTYLEDON (LEC) group of genes. The LEC genes encode proteins that also include LEC2, a B3 domain factor related to FUS3, and LEC1, a CCAAT box-binding factor. LEC1, LEC2, and FUS3 are essential for plant embryo development. All three loss-of-function mutants in Arabidopsis (Arabidopsis thaliana) prematurely exit embryogenesis and enter seedling developmental programs. When ectopically expressed, these genes promote embryo programs in seedlings. We report on chromatin immunoprecipitation-tiling array experiments to globally map binding sites for FUS3 that, along with other published work to assess transcriptomes in response to FUS3, allow us to determine direct from indirect targets. Many transcription factors associated with embryogenesis are direct targets of FUS3, as are genes involved in the seed maturation program. FUS3 regulates genes encoding microRNAs that, in turn, control transcripts encoding transcription factors involved in developmental phase changes. Examination of direct targets of FUS3 reveals that FUS3 acts primarily or exclusively as a transcriptional activator. Regulation of microRNA-encoding genes is one mechanism by which FUS3 may repress indirect target genes. FUS3 also directly up-regulates VP1/ABI3-LIKE1 (VAL1), encoding a B3 domain protein that functions as a repressor of transcription. VAL1, along with VAL2 and VAL3, is involved in the transition from embryo to seedling development. Many genes are responsive to FUS3 and to VAL1/VAL2 but with opposite regulatory consequences. The emerging picture is one of complex cross talk and interactions among embryo transcription factors and their target genes.

Pub.: 15 Jan '13, Pinned: 30 Sep '17

LEC1 sequentially regulates the transcription of genes involved in diverse developmental processes during seed development.

Abstract: LEAFY COTYLEDON1 (LEC1), an atypical subunit of the nuclear transcription factor Y (NF-Y) CCAAT-binding transcription factor, is a central regulator that controls many aspects of seed development including the maturation phase during which seeds accumulate storage macromolecules and embryos acquire the ability to withstand desiccation. To define the gene networks and developmental processes controlled by LEC1, genes regulated directly by and downstream of LEC1 were identified. We compared the mRNA profiles of wild-type and lec1-null mutant seeds at several stages of development to define genes that are down-regulated or up-regulated by the lec1 mutation. We used ChIP and differential gene-expression analyses in Arabidopsis seedlings overexpressing LEC1 and in developing Arabidopsis and soybean seeds to identify globally the target genes that are transcriptionally regulated by LEC1 in planta Collectively, our results show that LEC1 controls distinct gene sets at different developmental stages, including those that mediate the temporal transition between photosynthesis and chloroplast biogenesis early in seed development and seed maturation late in development. Analyses of enriched DNA sequence motifs that may act as cis-regulatory elements in the promoters of LEC1 target genes suggest that LEC1 may interact with other transcription factors to regulate distinct gene sets at different stages of seed development. Moreover, our results demonstrate strong conservation in the developmental processes and gene networks regulated by LEC1 in two dicotyledonous plants that diverged ∼92 Mya.

Pub.: 26 Jul '17, Pinned: 30 Sep '17