A genetic link between epigenetic repressor AS1-AS2 and a putative small subunit processome in leaf polarity establishment ofArabidopsis

Abstract

Although the DEAD-box RNA helicase family is ubiquitous in eukaryotes, its developmental role remains unelucidated. Here, we report that cooperative action between the Arabidopsis nucleolar protein RH10, an ortholog of human DEAD-box RNA helicase DDX47, and the epigenetic repressor complex of ASYMMETRIC-LEAVES1 (AS1) and AS2 (AS1-AS2) is critical to repress abaxial (ventral) genes ETT/ARF3 and ARF4, which leads to adaxial (dorsal) development in leaf primordia at shoot apices. Double mutations of rh10-1 and as2 (or as1) synergistically up-regulated the abaxial genes, which generated abaxialized filamentous leaves with loss of the adaxial domain. DDX47 is part of the small subunit processome (SSUP) that mediates rRNA biogenesis. In rh10-1 we found various defects in SSUP-related events, such as: accumulation of 35S/33S rRNA precursors; reduction in the 18S/25S ratio; and nucleolar hypertrophy. Double mutants of as2 with mutations of genes that encode other candidate SSUP-related components such as nucleolin and putative rRNA methyltransferase exhibited similar synergistic defects caused by up-regulation of ETT/ARF3 and ARF4. These results suggest a tight link between putative SSUP and AS1-AS2 in repression of the abaxial-determining genes for cell fate decisions for adaxial development.

Leaf morphology of progenies in Q. suber, Q. ilex, and their hybrids using multivariate and geometric morphometric analysis

“…Possibly, disruptions of regulatory networks due to interspecific genomic incompatibilities are responsible for producing abnormal phenotypes in Q. ilex × Q. suber progenies. As reported for the model species Arabidopsis, the repression of key genes that regulate the adaxial-abaxial polarity, such as ETT/ARF3, ARF4, and others that regulate the proximal-distal leaf length (class 1 KNOX homeobox genes -BP, KNAT2), produces asymmetric leaves (Matsumura et al 2016).…”

A genetic link between epigenetic repressor AS1–AS2 and DNA replication factors in establishment of adaxial–abaxial leaf polarity of <i>Arabidopsis</i>

“…Furthermore, transcript levels of ETT/ARF3 and ARF4 in the as2-1 icu2-1 double mutant were higher than those in both the as2-1 and icu2-1 single mutants (Figure 3). Since we have already shown that repression of expression of the abaxial genes ETT/ARF3 and ARF4 by AS1-AS2 and modifiers is important to form flat leaves Matsumura et al 2016; Takahashi et al Number of plants with trumpet-like or filamentous leaves is defined as the number of plants with more than one trumpet-like or filamentous leaves, respectively. Percentages in parenthesis indicate the frequency with which trumpet-like or filamentous leaves structure was observed relative to the total number of plants examined.…”

“…rfc3-1 mutant were narrow and pointed (Figure 4), which is one of characteristic leaf abnormalities by the modifier mutations to enhance leaf polarity defects in as1 and as2 (Matsumura et al 2016). To further confirm the involvement of AtRFC3 in the leaf polarity development, we examined leaf phenotypes in the double mutants as1-1 rfc3-1 and as2-1 rfc3-1.…”

“…Defects in polarity of as1 and as2 leaves are enhanced under certain growth conditions as well as in conjunction with mutations in members of certain groups of genes (Machida et al 2015), which are designated as modifiers of adaxial-abaxial patterning (Machida et al 2015;Matsumura et al 2016;Szakonyi et al 2010). To date, various modifier mutations that generate filamentous leaves surrounded by abaxialized epidermis in the as1 or as2 mutant backgrounds have been identified and it has been reported that the development of the adaxial domain of leaves is severely defective in those double mutants.…”

“…The modifier genes include several that mediate the biogenesis of tasiR-ARF (Machida et al 2015;Yang et al 2006). Other relevant modifier genes belong to several different groups: those for ribosome biogenesis (Horiguchi et al 2011a;Matsumura et al 2016;Pinon et al 2008;Yao et al 2008); chromatin modification (Kojima et al 2011;Ueno et al 2007); and cell proliferation (Horiguchi et al 2011b;Ishibashi et al 2012;Wang et al 2011;Xu et al 2012;Yuan et al 2010). Mutations of genes related to DNA replicationrelated chromatin remodeling and DNA repair have been identified as modifiers that enhance leaf adaxialabaxial abnormalities in as1 and as2 (Inagaki et al 2009;Machida et al 2015;Xu et al 2012).…”