In flowering plants, fruit dehiscence enables seed dispersal. Here we report that ntt-3D, an activation tagged allele of NO TRANSMITTING TRACT (NTT), caused a failure of fruit dehiscence in Arabidopsis. We identified ntt-3D, in which the 35S enhancer was inserted adjacent to AT3G-57670, from our activation tagged mutant library. ntt-3D mutants showed serrated leaves, short siliques, and indehiscence phenotypes. NTT-overexpressing plants largely phenocopied the ntt-3D plants. As the proximate cause of the indehiscence, ntt-3D plants exhibited a near absence of valve margin and lignified endocarp b layer in the carpel. In addition, the replum was enlarged in ntt-3D mutants. NTT expression reached a peak in flowers at stage 11 and gradually decreased thereafter and pNTT::GUS expression was mainly observed in the replum, indicating a potential role in fruit patterning. NTT:GFP localized in the nucleus and cytoplasm. FRUITFULL (FUL) expression was downregulated in ntt-3D mutants and ntt-3D suppressed upregulation of FUL in replumless mutants. These results indicate that NTT suppresses FUL, indicating a potential role in patterning of the silique. In seed crops, a reduction in pod dehiscence can increase yield by decreasing seed dispersal; therefore, our results may prove useful as a basis to improve crop yield.

Keywords: carpel development, dehiscent zone, endocarp b layer, fruit indehiscence, replum