Structure, gene composition, divergence time and phylogeny analysis of the woody desert species Neltuma alba, Neltuma chilensis and Strombocarpa strombulifera.

Neltuma alba (Algarrobo blanco), Neltuma chilensis (Algarrobo Chileno) and Strombocarpa strombulifera (Fortuna) are some of the few drought resistant trees and shrubs found in small highly fragmented populations, throughout the Atacama Desert. We reconstructed their plastid genomes using de novo assembly of paired-end reads from total genomic DNA. We found that the complete plastid genomes of N. alba and N. chilensis are larger in size compared to species of the Strombocarpa genus. The Strombocarpa species presented slightly more GC content than the Neltuma species. Therefore, we assume that Strombocarpa species have been exposed to stronger natural selection than Neltuma species. We observed high variation values in the number of cpSSRs (chloroplast simple sequence repeats) and repeated elements among Neltuma and Strombocarpa species. The p-distance results showed a low evolutionary divergence within the genus Neltuma, whereas a high evolutionary divergence was observed between Strombocarpa species. The molecular divergence time found in Neltuma and Strombocarpa show that these genera diverged in the late Oligocene. With this study we provide valuable information about tree species that provide important ecosystem services in hostile environments which can be used to determine these species in the geographically isolated communities, and keep the highly fragmented populations genetically healthy.

Isolation and Identification of Bacteria from Three Geothermal Sites of the Atacama Desert and Their Plant-Beneficial Characteristics.

The Region of Arica and Parinacota (Atacama Desert) offers several unexplored remote sites with unique characteristics that would allow for the formulation of new bioproducts for agriculture. Among them, Jurasi Hot Springs, Polloquere Hot Springs, and Amuyo Lagoons represent a group of open pools fed by thermal water springing from the mountains. Their microbiomes remain unspecified, providing a unique opportunity to characterize the endemic community of these sites and develop new bioproducts for sustainable agriculture. Bacteria were isolated from the sediments of these geothermal sites and characterized by sequencing the 16S rRNA gene, microbiological characterization, and agricultural functional characterization. A total of 57 bacteria were isolated from three geothermal sites north of the Atacama Desert. The sequence analysis showed that the isolates belong to several bacterial genera, including Pantoea, Bacillus, and Pseudomonas, among others. The functional characterization revealed the presence of PGP traits, hydrolytic enzymes, and biocontrol activity against phytopathogenic fungi. These bacteria possess the potential to develop new biobased products for agriculture in arid conditions.

Estatus taxonómico de Talides basistrigata Eaton, 1932 (Lepidoptera, Hesperiidae) y su reincorporación basados en una evaluación integrativa

Talides basistrigata Eaton, 1932, originalmente descrita de Perú, posteriormente fue transferida por Evans (1955) al género Hylephila Billberg, 1820, y considerada como una subespecie de H. phyleus (Drury, 1773), argumentando que basistrigata ocurre en ambientes más secos que los que habita phyleus. Actualmente se mantiene el rango taxonómico propuesto por Evans. El objetivo del presente trabajo es restituir el estatus taxonómico de especie válida para basistrigata con base en un análisis integrativo considerando aspectos morfológicos, ecológicos y genéticos. Se examinó las estructuras genitálicas en ejemplares de basistrigata y phyleus, se obtuvo secuencias del gen mitocondrial COI para ambas especies y se recopiló datos en campo para conocer su comportamiento de oviposición en los alrededores de Arequipa, suroeste de Perú. Como resultado del examen morfológico se halló diferencias notorias entre las estructuras genitálicas de ambas especies, principalmente en los procesos caudales de las valvas, la disposición de las pectinas y la forma del uncus en los machos. Con relación al análisis genético, se halló una distancia genética mayor a 3% entre ambas especies, apoyando así el estatus taxonómico de especie para basistrigata. Adicionalmente, desde una perspectiva ecológica, se registró que ambas especies utilizan distintos mecanismos de oviposición y diferentes plantas hospederas, exhibiendo además simpatría espacial y sincronía temporal en la vertiente occidental de los Andes en Perú. Se redescribe el macho y hembra adultos de basistrigata y se designa su lectotipo.

Talides basistrigata Eaton, 1932, originally described from Peru, was subsequently transferred to the genus Hylephila Billberg, 1820 by Evans (1955) and considered a subspecies of H. phyleus (Drury, 1773), arguing that basistrigata inhabits drier environments than phyleus. Currently, the taxonomic status proposed by Evans is retained. The aim of this study is to reinstate the taxonomic status of valid species for basistrigata based on an integrative analysis considering morphological, ecological, and genetic aspects. Genitalic structures were examined in specimens of both basistrigata and phyleus, mitochondrial COI gene sequences were obtained for both species, and field data were collected to understand their oviposition behaviour in the vicinity of Arequipa city, southwestern Peru. As a result of the morphological examination, notable differences were found between the male genitalia structures of both species, primarily in the caudal processes of the valvae, the arrangement of the pectines, and the shape of the uncus. Regarding the genetic analysis, a genetic distance of greater than 3% was observed between the two species, thus supporting the taxonomic status of species for basistrigata. Additionally, from an ecological perspective, it was recorded that both species employ distinct oviposition mechanisms and different host plants, exhibiting spatial sympatry and temporal synchrony on the western slope of the Andes in Peru. Male and female adults of basistrigata are redescribed, and a lectotype is designated.

Host Plant Variation and Lack of Genetic Differentiation in Populations of Dione (Agraulis) dodona Lamas & Farfán (Lepidoptera: Nymphalidae).

Dione (Agraulis) dodona (Nymphalidae: Heliconiinae) is a butterfly restricted to the western slopes of the Andes of Peru and Chile and is associated with Malesherbia tenuifolia in xerophytic environments. In this study, we found six additional species of host plants for D. (A.) dodona belonging to the genus Malesherbia (Passifloraceae). We used mitochondrial DNA sequences (COI) and microsatellites to screen genetic variation and investigate population structure in six geographic disjointed populations of D. (A.) dodona associated with distinct Malesherbia species. The PCoA analysis based on allele frequencies evidenced a lack of differentiation among populations and a low FST. The Bayesian cluster analyses revealed the existence of three genetically distinct groups, but almost all individuals present an admixture ancestry. An absence of isolation by distance pattern was observed. Possible scenarios are discussed: a bottleneck or recent colonization from interconnected populations from the south, and ongoing gene flow among local populations by high dispersal through a landscape formed of isolated populations of Malesherbia.

A contribution to the knowledge of leaf-mining Phyllocnistis Zeller, 1848 associated with Baccharis (Asteraceae), with description of two new species from Peru (Lepidoptera: Gracillariidae).

We provide new information on Neotropical Phyllocnistis Zeller (Gracillariidae) associated with Baccharis (Asteraceae) in the Andes region. Two new species are described, P. canta Cerdea Farfn, n. sp. and P. elongata Cerdea Farfn, n. sp., from the western slopes of the Andes of Peru between 2,000 and 3,000 m elevation, both associated with Baccharis latifolia (R.P.) Pers. The type locality of P. baccharidis Hering is confirmed; immature stages were found at 1,300 m feeding on Baccharis tucumanensis Hook. Arn. in Quebrada las Higueras (Tucumn, Argentina). Four new locality records for P. furcata Vargas Cerdea are provided, extending its distribution by 450 km to the north of the type locality.

An Endemic and Endangered New Species of the Lizard Liolaemus montanus Group from Southwestern Peru (Iguania: Liolaemidae), with a Key for the Species of the L. reichei Clade.

The southwestern Andes of Peru harbor a hidden taxonomic diversity of reptiles. We describe a new species of Liolaemus Wiegmann (Iguania: Liolaemidae) from xerophytic environments of the southwestern slopes of the Andes of Peru, 2,400-2,900 m asl. The new species, previously considered to be a population of L. insolitus Cei, exhibits unique diagnostic characters of morphology, scalation and color pattern, and molecular evidence that suggest that it belongs in the Liolaemus montanus species group and the L. reichei clade. Moreover, the species is endemic to the eastern slopes of La Caldera batholith in the Department of Arequipa, southern Peru. We also provide information on the conservation status of the species and suggest it be included in the IUCN red list of the threatened species as endangered (EN). A key for the species of the L. reichei clade is provided.

Chloroplast genome of Tillandsia landbeckii Phil. (Bromeliaceae) a species adapted to the hyper-arid conditions of the Atacama and Peruvian desert.

Tillandsia landbeckii Phil. is a vulnerable species belonging to the terrestrial Bromeliaceae family; it is highly adapted to extremely hyper-arid conditions of the Atacama Desert and Peruvian deserts. In this study, we sequenced, assembled, and annotated its chloroplast genome. T. landbeckii chloroplast genome is 159,131 bp in length, containing a large single-copy region of 87,164 bp, a small single-copy region of 18,521 bp, and a pair of inverted repeat regions of 26,723 bp. The GC content of the chloroplast genome is 37.33%. It encodes a total of 132 genes, including 86 protein-coding genes, 38 tRNA genes and 8 rRNA genes. The phylogenetic tree indicates that T. landbeckii is placed within the Bromeliaceae family and has a close relationship with T. marconae with 100% support.

A new species of Podanotum Torres & Johnson, 1996 (Lepidoptera, Lycaenidae) from northern Peru / Una nueva especie de Podanotum Torres & Johnson, 1996 (Lepidoptera, Lycaenidae) en el norte de Perú

Abstract We describe a new species of the genus Podanotum Torres & Johnson, 1996, Podanotum pajaten Farfán, Cerdeña & Bálint sp. nov. from northern Peru, associated with the Andean treeline ecotone adjacent to cloud forest and wet grassland at 3200 m above sea level. Description of this new species is based on one female adult and is distinguishable from its congeners by the combination of the following morphological characters: dorsal wing pale blue, forewing discoidal line present on ventral side, hindwing tailed, and ostium bursae distally toothed. Podanotum pajaten sp. nov. is separated geographically from the closest spatial species, P. glorissimum Bálint & Wojtusiak, 2002, by approximately 100 km to the south, and represents the second species described for Peru. An identification key to all known species of Podanotum is provided, stating their distributions by country.

Resumen Se describe una nueva especie del género Podanotum Torres & Johnson, 1996, Podanotum pajaten Farfán, Cerdeña & Bálint sp. nov. del norte de Perú, asociada al ecotono andino entre bosque nublado y pastizal húmedo a 3,200 metros de altitud. La descripción de esta nueva especie está basada en una hembra adulta que se distingue de sus congéneres por la combinación de los siguientes caracteres morfológicos: vista dorsal de las alas de color azul pálido, línea postdiscal del ala anterior presente en vista ventral, cola corta en ala posterior, y parte distal del ostium bursae dentada. Podanotum pajaten sp. nov. está separada geográficamente de la especie espacialmente más cercana, P. glorissimum Bálint & Wojtusiak, 2002, por aproximadamente 100 km hacia el sur, y representa la segunda especie descrita de Perú. Una clave de identificación es presentada para todas las especies conocidas de Podanotum, con indicación de los países de ocurrencia.

The Endophytic Pseudomonas sp. S57 for Plant-Growth Promotion and the Biocontrol of Phytopathogenic Fungi and Nematodes.

Oregano from Socoroma (Atacama Desert) is characterized by its unique organoleptic properties and distinctive flavor and it is produced using ancestral pesticide-free agricultural practices performed by the Aymara communities. The cultivation in this zone is carried out under extreme conditions where the standard production of different crops is limited by several environmental factors, including aridity, high concentration of salts, and boron among others. However, oregano plants are associated with microorganisms that mitigate biotic and abiotic stresses present in this site. In this work, the S57 strain (member of the Pseudomonas genus that is closely related to Pseudomonas lini) was isolated from roots of oregano plants, which are grown in soils with high content of non-sodium salts and aluminum. This bacterium stimulates the growth of Micro-Tom tomato plants irrigated with saline-boric water. Moreover, it controls the growth of phytopathogenic fungi Fusarium oxysporum and Botrytis cinerea and the nematode Meloidogyne incognita under saline-boric conditions. Together with the high levels of bacterial biomass (~47 g/L), these results allow the establishment of the bases for developing a potential new agricultural bioproduct useful for arid and semiarid environments where commercial biological products show erratic behavior.

LEA13 and LEA30 Are Involved in Tolerance to Water Stress and Stomata Density in Arabidopsis thaliana.

Late embryogenesis abundant (LEA) proteins are a large protein family that mainly function in protecting cells from abiotic stress, but these proteins are also involved in regulating plant growth and development. In this study, we performed a functional analysis of LEA13 and LEA30 from Arabidopsis thaliana. The results showed that the expression of both genes increased when plants were subjected to drought-stressed conditions. The insertional lines lea13 and lea30 were identified for each gene, and both had a T-DNA element in the regulatory region, which caused the genes to be downregulated. Moreover, lea13 and lea30 were more sensitive to drought stress due to their higher transpiration and stomatal spacing. Microarray analysis of the lea13 background showed that genes involved in hormone signaling, stomatal development, and abiotic stress responses were misregulated. Our results showed that LEA proteins are involved in drought tolerance and participate in stomatal density.

Chloroplast genome of Tillandsia marconae till & Vitek (Bromeliaceae), a hyperarid desert endangered species.

Tillandsia marconae Till & Vitek (Bromeliaceae) is a rare plant native species that grows over sand, in the coastal desert from Perú and Chile and is considered an endangered species. In this study, we assembled its chloroplast genome. The draft chloroplast genome of T. marconae is ca. 158,873 bp in length, containing a large single-copy region of 86,937 bp, a small single-copy region of 18,506 bp, and a pair of inverted repeat regions of 26,715 bp. The GC content of the draft chloroplast genome is 37.4%. It encodes a total of 135 genes, including 86 protein-coding genes, 38 tRNA genes, 8 rRNA genes, and three pseudogenes. The phylogenetic tree indicated that T. marconae is placed within the Bromeliaceae family and a close relationship with Tillandsia usneoides with 100% support.

Cryptic Diversity in the Monotypic Neotropical Micromoth Genus Angelabella (Lepidoptera: Gracillariidae) in the Peru-Chile Desert.

Angelabella (Lepidoptera: Gracillariidae: Oecophyllembiinae) is considered a monotypic Neotropical genus of leaf miner micromoths known only from a few valleys of the arid environments of the Peru-Chile desert, particularly the southernmost part of Peru and northernmost part of Chile (type locality), where natural populations of its primary host plant occur. The geographic distribution of potential host plants provides a scenario for a wider range for this micromoth genus. The aims of this study were to explore the geographic range of Angelabella, determine the spatial distribution of mitochondrial lineages, and test lineage conspecificity hypotheses. The spatial distribution of genetic diversity indicated the presence of four spatial clusters, three of which are north of the previously known geographic range. Genetic distances were 0.2-0.8% and 3.6-8.3% (K2P) between haplotypes of the same and different spatial clusters, respectively. Phylogenetic relationships indicated reciprocal monophyly among the four spatial clusters, suggesting that allopatric differentiation processes have governed the recent history of Angelabella in these arid environments. These groups were defined as different species by four species delimitation methods, suggesting that Angelabella is not a monotypic genus, but harbors at least four morphologically cryptic allopatric species with restricted geographic ranges, including the type species and three candidate species.

A new species of Ithome Chambers (Lepidoptera, Cosmopterigidae, Chrysopeleiinae) from the Atacama Desert revealed by morphology and DNA barcodes.

Morphology and DNA barcode sequences were used to assess the taxonomic status of a micro-moth of the genus Ithome Chambers, 1875 (Lepidoptera, Cosmopterigidae, Chrysopeleiinae), whose larvae feed on inflorescences of Prosopis tamarugo Phil. (Fabaceae), a tree native to the Pampa del Tamarugal, Atacama Desert, northern Chile. As a result, Ithome tamarugensis Vargas, sp. nov. is described and illustrated. Its genitalia are remarkably similar to those of Ithome tiaynai Vargas, 2004 from coastal valleys of the Atacama Desert. However, the two species can be recognized by the shape of the phallus in males and the shape of the antrum and ductus bursae in females. The genetic distance between DNA barcodes of I. tamarugensis and I. tiaynai was 3.0-3.3% (K2P), and a maximum likelihood analysis indicated that they are in reciprocally monophyletic clusters, providing additional support for the heterospecific status suggested by morphology.

Larva, pupa and DNA barcodes of the Neotropical geometrid moth Glena mielkei (Lepidoptera: Geometridae: Ennominae: Boarmiini)

ABSTRACT Glena mielkei Vargas, 2010 (Lepidoptera: Geometridae: Ennominae: Boarmiini) is a Neotropical geometrid moth native to the Atacama Desert of northern Chile whose larvae are folivorous on the shrub Trixis cacalioides (Asteraecae). The last instar and pupa are described and illustrated, and DNA barcode sequences are provided for the first time for G. mielkei. Descriptions are made based on larvae collected in the type locality. Comparisons with the available descriptions of congeneric species suggest that the chaetotaxy of the SV group of the abdominal segment and the morphology of the cremaster could be useful tools to species identification based on last instar and pupa, respectively. A search in BOLD (Barcode of Life Data System) showed that the only DNA barcode haplotype found in the two specimens sequenced was closest to Physocleora Warren, 1897 than Glena Hulst, 1896. These results coincide with the morphological peculiarities of the genitalia highlighted in the original description of G. mielkei, suggesting that a definitive assessment of the generic status of this geometrid moth deserves further integrative studies.

Long Non-Coding RNAs Responsive to Salt and Boron Stress in the Hyper-Arid Lluteño Maize from Atacama Desert.

Long non-coding RNAs (lncRNAs) have been defined as transcripts longer than 200 nucleotides, which lack significant protein coding potential and possess critical roles in diverse cellular processes. Long non-coding RNAs have recently been functionally characterized in plant stress-response mechanisms. In the present study, we perform a comprehensive identification of lncRNAs in response to combined stress induced by salinity and excess of boron in the Lluteño maize, a tolerant maize landrace from Atacama Desert, Chile. We use deep RNA sequencing to identify a set of 48,345 different lncRNAs, of which 28,012 (58.1%) are conserved with other maize (B73, Mo17 or Palomero), with the remaining 41.9% belonging to potentially Lluteño exclusive lncRNA transcripts. According to B73 maize reference genome sequence, most Lluteño lncRNAs correspond to intergenic transcripts. Interestingly, Lluteño lncRNAs presents an unusual overall higher expression compared to protein coding genes under exposure to stressed conditions. In total, we identified 1710 putatively responsive to the combined stressed conditions of salt and boron exposure. We also identified a set of 848 stress responsive potential trans natural antisense transcripts (trans-NAT) lncRNAs, which seems to be regulating genes associated with regulation of transcription, response to stress, response to abiotic stimulus and participating of the nicotianamine metabolic process. Reverse transcription-quantitative PCR (RT-qPCR) experiments were performed in a subset of lncRNAs, validating their existence and expression patterns. Our results suggest that a diverse set of maize lncRNAs from leaves and roots is responsive to combined salt and boron stress, being the first effort to identify lncRNAs from a maize landrace adapted to extreme conditions such as the Atacama Desert. The information generated is a starting point to understand the genomic adaptabilities suffered by this maize to surpass this extremely stressed environment.

Genetic divergence of isolated populations of the native micromoth Bucculatrix mirnae (Lepidoptera: Bucculatricidae) in the arid environments of Northern Chile.

Analysis of maternally inherited genes is especially helpful in population studies of host-specialized insects, as female dispersal is key to find an adequate host plant to ensure larval survival. Bucculatrix mirnae (Lepidoptera: Bucculatricidae) is a little-known Neotropical micromoth native to the arid environments of northern Chile whose hypermetamorphic larvae are miners and skeletonizers on leaves of two species of Baccharis (Asteraceae) shrubs. This micromoth has been detected in three isolated locations embracing a narrow geographic range: two from the coastal valleys of the Atacama Desert near sea level and one from the western slopes of the Andes at about 3000 m elevation. As the dispersal of B. mirnae is mostly restricted to the small adult stage, the altitudinal gradient and desert areas among the three localities could be effective barriers, triggering genetic differentiation among populations. Sequences of the DNA barcode fragment of the cytocrome oxidase subunit I mitochondrial gene were analyzed to assess for the first time the patterns of genetic variation of B. mirnae. Fifteen haplotypes, each exclusive to one locality, were found in the 71 specimens analyzed. Genetic divergence (K2P) between haplotypes of different localities was at least 2.0%. A Bayesian analysis with sequences of congeneric species grouped all the B. mirnae haplotypes in a clade, in which three well-supported locality-specific haplogroups were found. In concordance with this pattern, an analysis of molecular variance showed that the highest genetic variation was found among populations. Furthermore, all the population pairwise comparisons (FST) were significant. These results suggest that female migration between isolated populations of B. mirnae is absent. This pattern must be considered in the current scenario of habitat destruction and modification in the arid environments of northern Chile.

Genetic divergence of a newly documented population of the cecidogenous micromoth Eugnosta azapaensis Vargas & Moreira (Lepidoptera: Tortricidae) in the Atacama Desert of northern Chile

Abstract Eugnosta azapaensis Vargas and Moreira, 2015 (Lepidoptera: Tortricidae) is a micromoth native to the Atacama Desert whose larvae induce fusiform galls in shoots of Baccharis salicifolia (Ruiz & Pav.) Pers. (Asteraceae). The presence of this cecidogenous tortricid was previously recorded only from the type locality, the Azapa Valley, Arica Province, northern Chile. However, fusiform galls on shoots of B. salicifolia were recently found in Chaca, another coastal valley of the Atacama Desert. The adults obtained from these galls were preliminarily identified as E. azapaensis based on morphology. Subsequently, to assess an additional source of evidence for the taxonomic identification of E. azapaensis in this new locality, sequences of the DNA barcode fragment of the cytochrome oxidase subunit I mitochondrial gene from the two localities were analyzed. Four haplotypes were detected, two restricted to Azapa and two restricted to Chaca. The genetic divergence (K2P) between haplotypes of each locality was 0.2-0.8%, while it was 1.1-1.4% between haplotypes of different localities, and 8.7-13.5% between the Chilean haplotypes and other species of Eugnosta Hübner, 1825. In addition, all the sequences of Azapa and Chaca were clustered in a well-supported group in a Maximum Likelihood (ML) analysis. Accordingly, divergence and ML analyses support the morphological identification of E. azapaensis in the Chaca Valley. Furthermore, although preliminary, the analyses suggest that the genetic variation of the populations of this insect could be geographically structured, a pattern that must be assessed in further studies.

Prey identification in nests of the potter wasp Hypodynerus andeus (Packard) (Hymenoptera, Vespidae, Eumeninae) using DNA barcodes

Prey identification in nests of the potter wasp Hypodynerus andeus (Packard) (Hymenoptera, Vespidae, Eumeninae) using DNA barcodes. Geometrid larvae are the only prey known for larvae of the Neotropical potter wasp Hypodynerus andeus (Packard, 1869) (Hymenoptera, Vespidae, Eumeninae) in the coastal valleys of the northern Chilean Atacama Desert. A fragment of the mitochondrial gene cytochrome oxidase c subunit 1 was amplified from geometrid larvae collected from cells of H. andeus in the Azapa Valley, Arica Province, and used to provide taxonomic identifications. Two species, Iridopsis hausmanni Vargas, 2007 and Macaria mirthae Vargas, Parra & Hausmann, 2005 were identified, while three others could be identified only at higher taxonomic levels, because the barcode reference library of geometrid moths is still incomplete for northern Chile.

Functional analysis of sporophytic transcripts repressed by the female gametophyte in the ovule of Arabidopsis thaliana.

To investigate the genetic and molecular regulation that the female gametophyte could exert over neighboring sporophytic regions of the ovule, we performed a quantitative comparison of global expression in wild-type and nozzle/sporocyteless (spl) ovules of Arabidopsis thaliana (Arabidopsis), using Massively Parallel Signature Sequencing (MPSS). This comparison resulted in 1517 genes showing at least 3-fold increased expression in ovules lacking a female gametophyte, including those encoding 89 transcription factors, 50 kinases, 25 proteins containing a RNA-recognition motif (RRM), and 20 WD40 repeat proteins. We confirmed that eleven of these genes are either preferentially expressed or exclusive of spl ovules lacking a female gametophyte as compared to wild-type, and showed that six are also upregulated in determinant infertile1 (dif1), a meiotic mutant affected in a REC8-like cohesin that is also devoided of female gametophytes. The sporophytic misexpression of IOREMPTE, a WD40/transducin repeat gene that is preferentially expressed in the L1 layer of spl ovules, caused the arrest of female gametogenesis after differentiation of a functional megaspore. Our results show that in Arabidopsis, the sporophytic-gametophytic cross talk includes a negative regulation of the female gametophyte over specific genes that are detrimental for its growth and development, demonstrating its potential to exert a repressive control over neighboring regions in the ovule.

CHR11, a chromatin-remodeling factor essential for nuclear proliferation during female gametogenesis in Arabidopsis thaliana.

Chromatin-remodeling factors regulate the establishment of transcriptional programs during plant development. Although 42 genes encoding members of the SWI2/SNF2 family have been identified in Arabidopsis thaliana, <10 have been assigned a precise function on the basis of a mutant phenotype, and none have been shown to play a specific role during the gametophytic phase of the plant life cycle. A. thaliana chromatin-remodeling protein 11 (CHR11) encodes an imitation of switch (ISWI)-like chromatin-remodeling protein abundantly expressed during female gametogenesis and embryogenesis in Arabidopsis. To determine the function of CHR11 in wild-type plants, we introduced a hairpin construct leading to the production of double-stranded RNA, which specifically degraded the endogenous CHR11 mRNA by RNA interference (RNAi). Transcription of the RNAi-inducing hairpin RNA was driven by either a constitutive cauliflower mosaic virus 35S promoter (CaMV35S) acting at most stages of the sporophytic phase or a newly identified specific promoter acting at the onset of the female gametophytic phase (pFM1). All adult transformants that constitutively lacked sporophytic CHR11 activity showed reduced plant height and small cotyledonary embryos with limited cell expansion. In contrast, RNAi lines in which CHR11 was specifically silenced at the onset of female gametogenesis (megagametogenesis) had normal height and embryo size but had defective female gametophytes arrested before the completion of the mitotic haploid nuclear divisions. These results show that CHR11 is essential for haploid nuclear proliferation during megagametogenesis and cell expansion during the sporophytic phase, demonstrating the functional versatility of SWI2/SNF2 chromatin-remodeling factors during both generations of the plant life cycle.