Article

Maternal control of seed size by EOD3/CYP78A6 in Arabidopsis thaliana

State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
The Plant Journal (Impact Factor: 5.97). 01/2012; 70(6):929-39. DOI: 10.1111/j.1365-313X.2012.04907.x
Source: PubMed

ABSTRACT

Seed size in higher plants is coordinately determined by the growth of the embryo, endosperm and maternal tissue, but relatively little is known about the genetic and molecular mechanisms that set final seed size. We have previously demonstrated that Arabidopsis DA1 acts maternally to control seed size, with the da1-1 mutant producing larger seeds than the wild type. Through an activation tagging screen for modifiers of da1-1, we have identified an enhancer of da1-1 (eod3-1D) in seed size. EOD3 encodes the Arabidopsis cytochrome P450/CYP78A6 and is expressed in most plant organs. Overexpression of EOD3 dramatically increases the seed size of wild-type plants, whereas eod3-ko loss-of-function mutants form small seeds. The disruption of CYP78A9, the most closely related family member, synergistically enhances the seed size phenotype of eod3-ko mutants, indicating that EOD3 functions redundantly with CYP78A9 to affect seed growth. Reciprocal cross experiments show that EOD3 acts maternally to promote seed growth. eod3-ko cyp78a9-ko double mutants have smaller cells in the maternal integuments of developing seeds, whereas eod3-1D forms more and larger cells in the integuments. Genetic analyses suggest that EOD3 functions independently of maternal factors DA1 and TTG2 to influence seed growth. Collectively, our findings identify EOD3 as a factor of seed size control, and give insight into how plants control their seed size.

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Available from: Wenjuan Fang, Mar 23, 2015
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    • "The maternal parent contributes to the offspring seed phenotype in multiple ways including providing photosynthate and nutrients to support development, co-ordinating developmental timing, as well as imprinting of maternal gametes. The maternal plant affects seed size via (i) the seed coat, which comprises the maternal genotype and imposes mechanical constraints on seed development; (ii) maternal provisioning during seed development; (iii) maternal determination of progeny plasticity in response to developmental signals and environmental cues; and (iv) the effect of the triploid endosperm where gene imprinting occurs most often (Roach and Wulff, 1987;Platenkamp and Shaw, 1993;Adamski et al., 2009;Donohue, 2009;Fang et al., 2012). Maternal nutrient allocation is important for seed development. "
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    ABSTRACT: Seed size is an important component of grain yield and a key determinant trait for crop domestication. The Krug Yellow Dent long-term selection experiment for large and small seed provides a valuable resource to dissect genetic and phenotypic changes affecting seed size within a common genetic background. In this study, inbred lines derived from Krug Large Seed (KLS) and Krug Small Seed (KSS) populations and reciprocal F1 crosses were used to investigate developmental and molecular mechanisms governing seed size. Seed morphological characteristics showed striking differences between KLS and KSS inbred lines, and the reciprocal cross experiment revealed a strong maternal influence on both seed weight and seed size. Quantification of endosperm area, starchy endosperm cell size, and kernel dry mass accumulation indicated a positive correlation between seed size, endosperm cell number, and grain filling rate, and patterns of grain filling in reciprocal crosses mirrored that of the maternal parent. Consistent with the maternal contribution to seed weight, transcriptome profiling of reciprocal F1 hybrids showed substantial similarities to the maternal parent. A set of differentially expressed genes between KLS and KSS inbreds were found, which fell into a broad number of functional categories including DNA methylation, nucleosome assembly, and heat stress response. In addition, gene co-expression network analysis of parental inbreds and reciprocal F1 hybrids identified co-expression modules enriched in ovule development and DNA methylation, implicating these two processes in seed size determination. These results expand our understanding of seed size regulation and help to uncover the developmental and molecular basis underlying maternal control of seed size in maize.
    Full-text · Article · Jan 2016 · Journal of Experimental Botany
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    • "In Arabidopsis thaliana and rice, several CYP78As have been implicated in the control of seed development. For example, CYP78A6, CYP78A8 and CYP78A9 exhibit redundant functions in controlling floral organ growth and integument development by promoting cell proliferation in Arabidopsis (Fang et al., 2012; Sotelo-Silveira et al., 2013). Overexpression of these genes increases Arabidopsis seed size. "
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    ABSTRACT: Seed size is an important agronomic trait and a major component of seed yield in wheat. However, little is known about the genes and mechanisms that determine the final seed size in wheat. Here, we isolated TaCYP78A5, the orthologous gene of Arabidopsis CYP78A5/KLUH in wheat, from wheat cv. Shaan 512 and demonstrated that the expression of TaCYP78A5 affects seed size. TaCYP78A5 encodes the cytochrome P450 (CYP) 78A5 protein in wheat and rescued the phenotype of the Arabidopsis deletion mutant cyp78a5. By affecting the extent of integument cell proliferation in the developing ovule and seed, TaCYP78A5 influenced the growth of the seed coat, which appears to limit seed growth. TaCYP78A5 silencing caused a 10% reduction in cell numbers in the seed coat, resulting in a 10% reduction in seed size in wheat cv. Shaan 512. By contrast, the overexpression of TaCYP78A5 increased the number of cells in the seed coat, resulting in seed enlargement of ~11–35% in Arabidopsis. TaCYP78A5 activity was positively correlated with the final seed size. However, TaCYP78A5 overexpression significantly reduced seed set in Arabidopsis, possibly due to an ovule development defect. TaCYP78A5 also influenced embryo development by promoting embryo integument cell proliferation during seed development. Accordingly, a working model of the influence of TaCYP7A5 on seed size was proposed. This study provides direct evidence that TaCYP78A5 affects seed size and is a potential target for crop improvement.
    Full-text · Article · Dec 2015 · Journal of Experimental Botany
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    • "It has been shown that CYP78A family members are involved in reduced fertility; functional deletion or overexpression of CYP78A members led to a reduced seed set (Ito and Meyerowitz, 2000; Adamski et al., 2009; Fang et al., 2012; Sotelo-Silveira et al., 2013). All these reductions in fertility involved the female reproductive organ. "
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