Local maternal control of seed size by KLUH / CYP78A5 -dependent growth signaling

Abstract

Seed development in plants involves the coordinated growth of the embryo, endosperm, and maternal tissue. Several genes have been identified that influence seed size by acting maternally, such as AUXIN RESPONSE FACTOR2, APETALA2, and DA1. However, given the lack of gain-of-function effects of these genes on seed size, it is unclear whether their activity levels are limiting in WT plants and whether they could thus be used to regulate seed size in development or evolution. Also, whether the altered seed sizes reflect local gene activity or global physiological changes is unknown. Here, we demonstrate that the cytochrome P450 KLUH (KLU) regulates seed size. KLU acts locally in developing flowers to promote seed growth, and its activity level is limiting for seed growth in WT. KLU is expressed in the inner integument of developing ovules, where it non-cell autonomously stimulates cell proliferation, thus determining the growth potential of the seed coat and seed. A KLU-induced increase in seed size leads to larger seedlings and higher relative oil content of the seeds. Genetic analyses indicate that KLU acts independently of other tested maternal factors that influence integument cell proliferation. Thus, the level of KLU-dependent growth factor signaling determines size in ovules and seeds, suggesting this pathway as a target for crop improvement.Arabidopsis ͉ clonal analysis ͉ cytochrome P450 ͉ seed growth S eed size in higher plants is an important trait with respect to ecology and agriculture (1). For example, larger seeds are less easily dispersed, but offer the germinating seedling a larger supply of nutrients, thus increasing its competitiveness during seedling establishment and tolerance to adverse environmental conditions. At the same time, limited resources in the mother plant generally cause a tradeoff between the number and size of the seeds produced (2). As for agriculture, increasing seed size has been a crucial contributor to the yield increases in crop plants during domestication (3).Seeds are formed by the coordinated growth of maternal sporophytic and zygotic tissues (4). The zygotic tissues are the result of double fertilization, with one sperm cell fertilizing the diploid central cell to yield the triploid endosperm and the other sperm cell fertilizing the haploid egg cell to give rise to the diploid embryo. These maternal gametes lie within the embryo sac that develops in the nucellus region of the ovule (5). The nucellus is surrounded by the integuments, protective organs that form the maternal component of the mature seed after fertilization, the seed coat (6).The size of seeds is known to be influenced by parent-of-origin effects, with a paternal genome excess causing seed overgrowth, whereas a maternal genome excess reduces seed size (7). In addition, recent genetic studies in the model species Arabidopsis thaliana and rice have identified a number of factors affecting seed size by acting in the maternal and/or zygotic tissues. Among the zygotically acting factors, a small cascade of genes ...

A cytochrome P450 regulates a domestication trait in cultivated tomato

“…ORF6 encodes a protein with the highest similarity to the Arabidopsis KLUH/CYP78A5 protein controlling vegetative and reproductive organ size, and also seed size (22,24). Other members of this subfamily of cytochrome P450 also control organ and plant size, e.g., CYP78A9, CYP78A6…”

Natural variation in ARF18 gene simultaneously affects seed weight and silique length in polyploid rapeseed

“…In Arabidopsis, some mutants such as ap2, arf2, da1, eod3, ttg2, and klu control seed size mainly by regulating cell elongation in the integument surrounding the seed (1)(2)(3)(4)(5). In mini3, iku1, iku2, and shb1 mutants, premature cellularization or proliferation of the endosperm in the early phase of seed development affects seed mass (6)(7)(8)(9)(10).…”

Descripción de semillas silvestres de Euphorbia strigosa Hook and Arn del estado de Nayarit, México

“…2005) or crosstalk between maternal inheritance and zygotic controls that regulate in coordinated seed size (García et al 2005). It is suggested that integument growth limits final seed size (Adamski et al 2009). On the other hand, there is the hypothesis that seed size evolves as part of a spectrum of life history traits, including plant size, plant longevity, juvenile survival rate and time to reproduction (Moles y Westoby 2006).…”