NAC Family Proteins NARS1/NAC2 and NARS2/NAM in the Outer Integument Regulate Embryogenesis inArabidopsis

Abstract

Seed morphogenesis consists of embryogenesis and the development of maternal tissues such as the inner and outer integuments, both of which give rise to seed coats. We show that expression of chimeric repressors derived from NAC-REGULATED SEED MORPHOLOGY1 and -2 (NARS1 and NARS2, also known as NAC2 and NAM, respectively) caused aberrant seed shapes in Arabidopsis thaliana. Double knockout mutant nars1 nars2 exhibited abnormally shaped seeds; moreover, neither nars1 nor nars2 produced abnormal seeds, indicating that NARS1 and NARS2 redundantly regulate seed morphogenesis. Degeneration of the integuments in nars1 nars2 was markedly delayed, while that of the wild type occurred around the torpedo-shaped embryo stage. Additionally, nars1 nars2 showed a defect in embryogenesis: some nars1 nars2 embryos were developmentally arrested at the torpedo-shaped embryo stage. Unexpectedly, however, neither NARS1 nor NARS2 was expressed in the embryo at this stage, although they were found to be expressed in the outer integument. Wild-type pistils pollinated with nars1 nars2 pollen generated normal seeds, while the reverse crossing generated abnormal seeds. Taken together, these results indicate that NARS1 and NARS2 regulate embryogenesis by regulating the development and degeneration of ovule integuments. Our findings suggest that there is an intertissue communication between the embryo and the maternal integument.

Differential expression analysis of transcripts related to oil metabolism in maturing seeds of Jatropha curcas L.

“…A complex network of transcription factors control gene expression programs necessary for seed maturation (Baud and Lepiniec 2010). In this context, detection of very high transcript levels for putative NAC family transcription factor in JC1 indicates the importance of the same in regulating early embryogenesis as reported in Arabidopsis (Kunieda et al 2008). Higher representation of transcripts related to senescence associated proteins may be attributed to the abundance of this transcript (Fig.…”

Biosynthesis of volatile terpenes that accumulate in the secretory cavities of young leaves of Japanese pepper (<i>Zanthoxylum piperitum</i>): Isolation and functional characterization of monoterpene and sesquiterpene synthase genes

“…To observe the development of secretory cavities, immature and mature leaves were cleared by incubation in 10: 2.5: 1 chloral hydrate:water:glycerol (w/v/w) solution. They were inspected using a different interference contrast microscope (ECLIPSE Ni; Nikon) (Kunieda et al 2008). The secretory cavity radius (r) was measured under microscope and secretory cavity volume (V) was estimated with the equation: V=4/3πr 3…”

Networks controlling seed size in Arabidopsis

“…Two cell layers derive from the outer integument 323 (oi) and three from the inner one (ii). The outer integument 324 consists of two cell layers (oi1 and oi2), and the inner 325 integument consists of three cell layers (ii1, ii1 0 and ii2) 326 (Beeckman et al 2000; Kunieda et al 2008 …”