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Abstract

Sperm cells of mature pollen possess a distinct transcriptome and it is therefore conceivable that some of these transcripts might be delivered to the zygote during fertilization. The impact of such paternal factors on fertilization and early seed development, however, is poorly understood. Recently, we described the Pelle/IRAK-like cytoplasmic kinase SHORT SUSPENSOR that links the onset of embryogenesis with the fertilization event by a novel parent-of-origin effect. To identify novel mutants with similar effect on early seed development, we conducted a forward genetic screen for paternal effect mutants. Individual M2 plants of an EMS mutagenized plant population were used as pollen donor, while a conditionally male-sterile mutant was used as female crossing partner to circumvent manual emasculation. Seed set was recorded ~72h after pollination and immature seed were dissected and cleared for visual inspection of embryo and endosperm development by DIC microscopy. In total, over 3000 M2 plants were screened this way and so far 34 candidates showed reproducible defects in seed and/or embryo development after crossing. The majority of mutants seems to affect the fertilization process itself and comprises presumably gametophytic mutants. Four of the candidates, however, show defects in embryo or endosperm after fertilization. Here, we report first results for some of these candidates.