Seedless fruit in Annona squamosa L. is monogenic and conferred by INO locus deletion in multiple accessions.

Inheritance of the presence/absence of seeds in Annona squamosa is mediated by a single fully recessive gene and is caused by a deletion of the INNER NO OUTER (INO) locus. For some fruits, seedless varieties are desirable for consumption and processing. In the sugar apple tree (Annona squamosa L.

The Arabidopsis () gene acts exclusively and quantitatively in regulation of ovule outer integument development.

The () gene is essential for formation of the outer integument of ovules in . Initially described lesions in were missense mutations resulting in aberrant mRNA splicing. To determine the null mutant phenotype, we generated frameshift mutations and found, in confirmation of results on another recently identified frameshift mutation, that such mutants have a phenotype identical to the most severe splicing mutant (), with effects specific to outer integument development.

Functional conservation of the grapevine candidate gene INNER NO OUTER for ovule development and seed formation.

Seedlessness represents a highly appreciated trait in table grapes. Based on an interesting case of seedless fruit production described in the crop species Annona squamosa, we focused on the Vitis vinifera INNER NO OUTER (INO) gene as a candidate. This gene encodes a transcription factor belonging to the YABBY family involved in the determination of abaxial identity in several organs.

Development and evolution of the unique ovules of flowering plants.

Ovules are the precursors to seeds and as such are critical to plant propagation and food production. Mutant studies have led to the identification of numerous genes regulating ovule development. Genes encoding transcription factors have been shown to direct ovule spacing, ovule identity and integument formation.

Integument Development in Depends on Interaction of YABBY Protein INNER NO OUTER with Coactivators and Corepressors.

INNER NO OUTER (INO) is a YABBY protein that is essential for the initiation and development of the outer integument of ovules. Other YABBY proteins have been shown to be involved in both negative and positive regulation of expression of putative target genes. YABBY proteins have also been shown to interact with the corepressor LEUNIG (LUG) in several systems.

Conservation of the role of INNER NO OUTER in development of unitegmic ovules of the Solanaceae despite a divergence in protein function.

Background: The INNER NO OUTER (INO) gene is expressed in the outermost cell layer of the outer integument of bitegmic ovules and is essential for this organ's growth. The role and cross-species functional conservation of INO orthologs were examined in members of the Solanaceae, which have unitegmic ovules. Unitegmy has evolved several times in disparate angiosperm lineages.

CORONA, PHABULOSA and PHAVOLUTA collaborate with BELL1 to confine WUSCHEL expression to the nucellus in Arabidopsis ovules.

Angiosperm ovules consist of three proximal-distal domains - the nucellus, chalaza and funiculus - demarcated by developmental fate and specific gene expression. Mutation in three paralogous class III homeodomain leucine zipper (HD-ZIPIII) genes leads to aberrations in ovule integument development. Expression of WUSCHEL (WUS) is normally confined to the nucellar domain, but in this triple mutant expression expands into the chalaza.

Positive- and negative-acting regulatory elements contribute to the tissue-specific expression of INNER NO OUTER, a YABBY-type transcription factor gene in Arabidopsis.

Background: The INNER NO OUTER (INO) gene, which encodes a YABBY-type transcription factor, specifies and promotes the growth of the outer integument of the ovule in Arabidopsis. INO expression is limited to the abaxial cell layer of the developing outer integument of the ovule and is regulated by multiple regions of the INO promoter, including POS9, a positive element that when present in quadruplicate can produce low-level expression in the normal INO pattern.

Results: Significant redundancy in activity between different regions of the INO promoter is demonstrated.

ETTIN (ARF3) physically interacts with KANADI proteins to form a functional complex essential for integument development and polarity determination in Arabidopsis.

KANADI (KAN) transcription factors promote abaxial cell fate throughout plant development and are required for organ formation during embryo, leaf, carpel and ovule development. ABERRANT TESTA SHAPE (ATS, or KAN4) is necessary during ovule development to maintain the boundary between the two ovule integuments and to promote inner integument growth. Yeast two-hybrid assays identified ETTIN (ETT, or AUXIN RESPONSE FACTOR 3) as a transcription factor that could physically interact with ATS.

Seed dispersal: same gene, different organs.

A single nucleotide change in a conserved promoter element is responsible for both human-selected retention of rice grains on pedicels and for naturally selected differences in dehiscence-associated fruit structures in mustards.

Ancestral expression patterns and evolutionary diversification of YABBY genes in angiosperms.

Lateral organ growth in seed plants is controlled in part by members of the YABBY (YAB) and class III homeodomain/leucine zipper (HD-ZIPIII) families of transcription factors. HD-ZIPIII genes appear to play a conserved role in such organs, but YAB genes have diversified, with some members of the family having specialized functions in leaves, carpels or ovule integuments. The ancestral expression patterns and timing of divergence of the various classes of YAB genes remain to be established.

Seedless fruits and the disruption of a conserved genetic pathway in angiosperm ovule development.

Although the biological function of fruiting is the production and dissemination of seeds, humans have developed seedless fruits in a number of plant species to facilitate consumption. Here we describe a unique spontaneous seedless mutant (Thai seedless; Ts) of Annona squamosa (sugar apple), a member of the early-divergent magnoliid angiosperm clade. Ovules (seed precursors) of the mutant lack the outer of two normal integuments, a phenocopy of the inner no outer (ino) mutant of Arabidopsis thaliana.

Expression of ovule and integument-associated genes in reduced ovules of Santalales.

Santalales comprise mainly parasitic plants including mistletoes and sandalwoods. Bitegmic ovules similar to those found in most other angiosperms are seen in many members of the order, but other members exhibit evolutionary reductions to the unitegmic and ategmic conditions. In some mistletoes, extreme reduction has resulted in the absence of emergent ovules such that embryo sacs appear to remain embedded in placental tissues.

Ovule development: genetic trends and evolutionary considerations.

Much of our current understanding of ovule development in flowering pants is derived from genetic and molecular studies performed on Arabidopsis thaliana. Arabidopsis has bitegmic, anatropous ovules, representing both the most common and the putative ancestral state among angiosperms. These studies show that key genetic determinants that act to control morphogenesis during ovule development also play roles in vegetative organ formation, consistent with Goethe's "everything is a leaf" concept.

Gene regulation in parthenocarpic tomato fruit.

Parthenocarpy is potentially a desirable trait for many commercially grown fruits if undesirable changes to structure, flavour, or nutrition can be avoided. Parthenocarpic transgenic tomato plants (cv MicroTom) were obtained by the regulation of genes for auxin synthesis (iaaM) or responsiveness (rolB) driven by DefH9 or the INNER NO OUTER (INO) promoter from Arabidopsis thaliana. Fruits at a breaker stage were analysed at a transcriptomic and metabolomic level using microarrays, real-time reverse transcription-polymerase chain reaction (RT-PCR) and a Pegasus III TOF (time of flight) mass spectrometer.

Expression-based discovery of candidate ovule development regulators through transcriptional profiling of ovule mutants.

Background: Arabidopsis ovules comprise four morphologically distinct parts: the nucellus, which contains the embryo sac, two integuments that become the seed coat, and the funiculus that anchors the ovule within the carpel. Analysis of developmental mutants has shown that ovule morphogenesis relies on tightly regulated genetic interactions that can serve as a model for developmental regulation. Redundancy, pleiotropic effects and subtle phenotypes may preclude identification of mutants affecting some processes in screens for phenotypic changes.

Roles of polarity determinants in ovule development.

Ovules are the female reproductive structures that develop into seeds. Angiosperm ovules include one, or more commonly two, integuments that cover the nucellus and female gametophyte. Mutations in the Arabidopsis KANADI (KAN) and YABBY polarity genes result in amorphous or arrested integument growth, suggesting that polarity determinants play key roles in ovule development.

Independence and interaction of regions of the INNER NO OUTER protein in growth control during ovule development.

The outer integument of the Arabidopsis (Arabidopsis thaliana) ovule develops asymmetrically, with growth and cell division occurring primarily along the region of the ovule facing the base of the gynoecium (gynobasal). This process is altered in the mutants inner no outer (ino) and superman (sup), which lead to absent or symmetrical growth of the outer integument, respectively. INO encodes a member of the YABBY family of putative transcription factors, and its expression is restricted to the gynobasal side of developing ovules via negative regulation by the transcription factor SUP.

Arabidopsis SHORT INTEGUMENTS 2 is a mitochondrial DAR GTPase.

The Arabidopsis short integuments 2-1 (sin2-1) mutant produces ovules with short integuments due to early cessation of cell division in these structures. SIN2 was isolated and encodes a putative GTPase sharing features found in the novel DAR GTPase family. DAR proteins share a signature DAR motif and a unique arrangement of the four conserved GTPase G motifs.

ABERRANT TESTA SHAPE encodes a KANADI family member, linking polarity determination to separation and growth of Arabidopsis ovule integuments.

The Arabidopsis aberrant testa shape (ats) mutant produces a single integument instead of the two integuments seen in wild-type ovules. Cellular anatomy and patterns of marker gene expression indicate that the single integument results from congenital fusion of the two integuments of the wild type. Isolation of the ATS locus showed it to encode a member of the KANADI (KAN) family of putative transcription factors, previously referred to as KAN4.

Mechanisms of derived unitegmy among Impatiens species.

Morphological transitions associated with ovule diversification provide unique opportunities for studies of developmental evolution. Here, we investigate the underlying mechanisms of one such transition, reduction in integument number, which has occurred several times among diverse angiosperms. In particular, reduction in integument number occurred early in the history of the asterids, a large clade comprising approximately one-third of all flowering plants.

Multiple protein regions contribute to differential activities of YABBY proteins in reproductive development.

Members of the YABBY family of putative transcription factors participate in abaxial-adaxial identity determination in lateral organs in Arabidopsis (Arabidopsis thaliana). Two YABBY genes specifically expressed in reproductive structures, CRABS CLAW (CRC) and INNER NO OUTER (INO), have additional activities, with CRC promoting nectary development and carpel fusion, and INO responding to spatial regulation by SUPERMAN during ovule development. All YABBY coding regions, except YABBY5, were able to restore outer integument growth in ino-1 mutants when expressed from the INO promoter (PRO(INO)).