Genome investigation suggestsMdSHN3, an APETALA2-domain transcription factor gene, to be a positive regulator of apple fruit cuticle formation and an inhibitor of russet development

Abstract

HighlightQTL analysis of an apple population identifies genomic regions linked to cuticle formation and subsequent russet formation. Further investigation suggests that MdSHN3 is a major regulator of cuticle biosynthesis in apple.

MYB107 and MYB9 Homologs Regulate Suberin Deposition in Angiosperms

“…The first, MdSHN3, encodes a putative positive transcriptional regulator of cutin deposition (Lashbrooke et al, 2015a) and the other a putative ortholog to an Arabidopsis ABCG transporter protein (AtABCG11) associated with the extracellular secretion of cutin and wax (Panikashvili et al, 2007;Falginella et al, 2015). In both cases, mutations leading to deficiency in the normal deposition of cuticle leads to russet formation.…”

“…In apple, russet is described as the suberization of the fruit surface that occurs developmentally following cuticular damage in some cultivars (Khanal et al, 2013;Lashbrooke et al, 2015a). A regular skinned clone of the apple cultivar Golden Delicious ('Reinders') was analyzed in conjunction with a clone deriving from a somatic mutation for this cultivar that shows highly russeted fruits ('Rugiada') ( Figure 2A).…”

“…Furthermore, the embedded waxes found in suberin often consist of alkyl ferulates, which are not typically found in cutin . This wound response suberin is typically brown and rough in appearance and can be seen on the surface of fruits, leaves, and stems, where it fulfills a similar role as the regular cuticle, although it is less elastic and typically a less efficient water barrier Lashbrooke et al, 2015a).…”

“…To date, no genes responsible for the extracellular polymerization of the suberin polymer or for the synthesis of the aromatic monomers have been described. While several transcription factors influencing plant cutin and wax formation have been identified Oshima et al, 2013;Shi et al, 2011Shi et al, , 2013Lashbrooke et al, 2015aLashbrooke et al, , 2015b, only a single regulatory gene of suberin synthesis has been characterized. The recently described MYB factor AtMYB41 was demonstrated to be a positive regulator of suberin biosynthesis in Arabidopsis thaliana under stress conditions.…”

“…The initial study of suberization in the wounded fruit skin surface of tomato (Solanum lycopersicum) and apple (Malus x domestica) led to the discovery of genes associated with developmentally regulated suberin deposition in multiple plant species. It appeared that the gene expression program as a consequence of russeting, a naturally occurring suberization phenomenon of apple surface (Khanal et al, 2013;Lashbrooke et al, 2015a), and suberization due to cuticular deficiency in tomato skin, is vastly analogous. Interrogating additional transcriptomics data sets associated with suberin formation uncovered a conserved gene expression signature associated with suberin monomer biosynthesis and polymer assembly.…”