LONO1Encoding a Nucleoporin Is Required for Embryogenesis and Seed Viability in Arabidopsis      

Abstract

Early embryogenesis in Arabidopsis (Arabidopsis thaliana) is distinguished by a predictable pattern of cell divisions and is a good system for investigating mechanisms of developmental pattern formation. Here, we identified a gene called LONO1 (LNO1) in Arabidopsis in which mutations can abolish the first asymmetrical cell division of the zygote, alter planes and number of cell divisions in early embryogenesis, and eventually arrest embryo development. LNO1 is highly expressed in anthers of flower buds, stigma papilla of open flowers, and embryo and endosperm during early embryogenesis, which is correlated with its functions in reproductive development. The homozygous lno1-1 seed is not viable. LNO1, a homolog of the nucleoporin NUP214 in human (Homo sapiens) and Nup159 in yeast (Saccharomyces cerevisiae), encodes a nucleoporin protein containing phenylalanineglycine repeats in Arabidopsis. We demonstrate that LNO1 can functionally complement the defect in the yeast temperaturesensitive nucleoporin mutant nup159. We show that LNO1 specifically interacts with the Arabidopsis DEAD-box helicase/ ATPase LOS4 in the yeast two-hybrid assay. Furthermore, mutations in AtGLE1, an Arabidopsis homolog of the yeast Gle1 involved in the same poly(A) mRNA export pathway as Nup159, also result in seed abortion. Our results suggest that LNO1 is a component of the nuclear pore complex required for mature mRNA export from the nucleus to the cytoplasm, which makes LNO1 essential for embryogenesis and seed viability in Arabidopsis.

InsP6-Sensitive Variants of the Gle1 mRNA Export Factor Rescue Growth and Fertility Defects of the ipk1 Low-Phytic-Acid Mutation in Arabidopsis

“…Plant Gle1 is involved in nuclear mRNA export by interacting with LOS4 to stimulate LOS4 ATPase/RNA helicase activity. Functions of Gle1 are essential for embryogenesis (Braud et al, 2012) and critical for the postembryonic growth of plants (Figure 1), which is reminiscent of essential Gle1 functions in both yeast and mammals (Murphy and Wente, 1996;Nousiainen et al, 2008). Montpetit et al (2011) recently proposed the molecular mechanism of Dbp5/Gle1-driven mRNA export in yeast.…”

“…Gle1 is also found in the cytosol and plays a role in translation initiation and termination in Dbp5-independent and -dependent manners, respectively (Bolger et al, 2008;Kutay and Panse, 2008). In plants, the cellular functions of Gle1 are unknown except that the T-DNA insertion mutation of Arabidopsis thaliana Gle1 causes an embryo lethal phenotype (Braud et al, 2012). Here, we reveal the cellular function of Gle1 in plants in relation to LOS4 and InsP 6 and show that modified Gle1 with increased InsP 6 sensitivity complements the ipk1 low-phytate mutation.…”

Identification and analysis of LNO1-Like and AtGLE1-Like Nucleoporins in plants

“…These proteins are vital and mutations in AtGLE1 and LNO1 result in non-viable seeds in Arabidopsis. 24 Both los4-1 and los4-2 mutants show abnormal mRNA localization, but are viable, 31 and this could be due to that both of los4-1 and los4-2 are missense mutations instead of null alleles. Therefore, it is tempting to speculate that a null allele of the los4 mutant might have a similar seed abortion phenotype as lno1 and Atgle1.…”

“…30 As in the Arabidopsis lno1 mutant, mutations in AtGLE1 also result in embryo abortion. 24 We have shown that LNO1 specifically interacts with LOW EXPRESSION OF OSMOTICALLY RESPONSIVE GENES 4 (LOS4) in a yeast two-hybrid assay. LOS4 encodes a DEAD box RNA helicase/ATPase in Arabidopsis.…”

“…27 We have shown that LNO1 in Arabidopsis, like NUP214 in mice, is required for embryogenesis, and that the homozygous lno1/lno1 seed is aborted. 24 AtGLE1, an Arabidopsis homolog of the yeast Gle1 involved in the same poly(A) mRNA export pathway as Nup159, was recently discovered. 15 Gle1 was first identified in yeast that contains a nuclear export signal.…”