Expression of ZmLEC1 and ZmWRI1 Increases Seed Oil Production in Maize    

Abstract

Increasing seed oil production is a major goal for global agriculture to meet the strong demand for oil consumption by humans and for biodiesel production. Previous studies to increase oil synthesis in plants have focused mainly on manipulation of oil pathway genes. As an alternative to single-enzyme approaches, transcription factors provide an attractive solution for altering complex traits, with the caveat that transcription factors may face the challenge of undesirable pleiotropic effects. Here, we report that overexpression of maize (Zea mays) LEAFY COTYLEDON1 (ZmLEC1) increases seed oil by as much as 48% but reduces seed germination and leaf growth in maize. To uncouple oil increase from the undesirable agronomic traits, we identified a LEC1 downstream transcription factor, maize WRINKLED1 (ZmWRI1). Overexpression of ZmWRI1 results in an oil increase similar to overexpression of ZmLEC1 without affecting germination, seedling growth, or grain yield. These results emphasize the importance of field testing for developing a commercial high-oil product and highlight ZmWRI1 as a promising target for increasing oil production in crops.

Enhanced Seed Oil Production in Canola by Conditional Expression of Brassica napus LEAFY COTYLEDON1 and LEC1-LIKE in Developing Seeds

“…A recent study showed seed-specific expression ZmWRI1, a WRI1-like gene of maize (Zea mays), enhanced oil accumulation in transgenic maize without detectable abnormalities. However, expression of ZmLEC1 under similar conditions severely affected growth and development of the resulting transgenic maize plants (Shen et al, 2010). Similar results were obtained by constitutive overexpression of the ZmWRI1 gene in the transgenic maize plants (Pouvreau et al, 2011).…”

“…A detailed analysis of major agronomic traits of the field-grown T3 homozygous plants revealed that the transgenic plants were phenotypically similar to Westar plants in most categories, including 1000-seed weight and the seed yield (Supplemental Table S1). Because AtLEC1 acts upstream of ABSCISIC ACID INSENSITIVE3, a key regulator of seed maturation and seed germination (Koornneef et al, 1984;Kagaya et al, 2005), and also because seed-specific expression of ZmLEC1 causes reduced seed germination (Shen et al, 2010), we compared the germination rate of the transgenic seeds with Westar seeds. No difference of the germination rate was found between Westar and the transgenic seeds (Supplemental Fig.…”

“…Overexpression of these genes results in an increased level of FAs in the transgenic Arabidopsis plants, accompanied by up-regulated expression of key FA synthetic genes as well as glycolytic genes (Stone et al, 2001;Kwong et al, 2003;Cernac and Benning, 2004;Baud et al, 2007;Mu et al, 2008). However, in most, if not all cases, overexpression of these transcription factor genes causes a variety of developmental abnormalities and even lethality (Lotan et al, 1998;Stone et al, 2001;Cernac and Benning, 2004;Wang et al, 2007;Mu et al, 2008;Shen et al, 2010). These detrimental effects render it difficult to directly utilize these genes in genetic improvement of oil-producing crops.…”

Truncation of LEAFY COTYLEDON1 Protein Is Required for Asexual Reproduction in Kalanchoë daigremontiana

“…These results are consistent with other analysis showing that ectopic expression of LEC1, FUSCA3 (FUS3), and LEC2 genes induces the accumulation of lipid and protein reserves characteristic of developing seeds in cells of vegetative and reproductive tissues (Lotan et al, 1998;Stone et al, 2001Stone et al, , 2008Santos-Mendoza et al, 2005). Moreover, seed-specific overexpression of maize (Zea mays) LEC1 (ZmLEC1) resulted in an average 35% increase in seed oil but reduced germination and vegetative growth in the field (Shen et al, 2010) In Arabidopsis, the seed maturation program is controlled by a network of transcription factors that includes the B3 domain transcription factors (ABA-INSENSITIVE3 [ABI3], FUS3, and LEC2; Giraudat et al, 1992;Luerssen et al, 1998;Stone et al, 2001) and two LEC1-type HAP3 family CCAAT-binding factors, LEC1 and L1L (Lotan et al, 1998;Kwong et al, 2003). Given that these transcription factors have strong positive roles in promoting seed-specific programs, mechanisms have evolved to ensure that their expression is suppressed during vegetative growth.…”

Compartmentation of Triacylglycerol Accumulation in Plants

“…Thus, WRI1 can be considered as a "master regulator" that controls transcription of almost all key enzymes that convert sucrose to FA. The importance of WRI1 was confirmed when seed oil was increased by 30% in field trials of maize that overexpress WRI1 (12), an increase that would be valued at $2 billion if extended to all maize production in the United States. In addition to controlling oil production in seeds, recent evidence indicates that WRI1 is likely a major factor responsible for the extremely high oil content (up to 90% of tissue weight) produced by oil palm mesocarp.…”