Multiple Inflorescence Research Articles

The receptor kinase OsANX limits precocious flowering and inflorescence over-branching and maintains pollen tube integrity in rice

CrRLK1L subfamily members are involved in diverse growth- and development-related processes in Arabidopsis. However, the functions of their counterparts in rice are unknown. Here, OsANX expression was detected in developing inflorescences, mature pollen grains, and growing pollen tubes, and it was localized to the plasma membrane in pollen grains and tobacco epidermal cells. Homozygous osanx progeny could not be segregated from the CRISPR/Cas9-edited mutants osanx-c1+/- and osanx-c2+/-, and such progeny were segregated only occasionally from osanx-c3+/-. Further, all three alleles showed osanx male but not female gamete transmission defects, in line with premature pollen tube rupture in osanx-c3. Additionally, osanx-c3 exhibited precocious flowering, excessively branched inflorescences, and an extremely low seed setting rate of 1.4 %, while osanx-c2+/- and osanx-c3+/- had no obvious defects in inflorescence development or the seed setting rate compared to wild-type Nipponbare (Nip). Consistent with this, the complemented line pPS1:OsANX-GFP/osanx-c2 (PSC), in which the lack of OsANX expression was inflorescence-specific, showed slightly earlier flowering and overly-branched panicles. Multiple inflorescence meristem transition-related and inflorescence architecture-related genes were expressed at higher levels in osanx-c3 than in Nip; thus, they may partially account for the aforementioned mutant phenotypes. Our findings broaden our understanding of the biological functions of OsANX in rice.

Comparative transcriptomic analysis provides insights into the development of a Salvia splendens Ker-Gawler mutant, SX919M.

Salvia splendens is a perennial, ornamental herbaceous flower that is widely cultivated as a bedding plant in gardens. The development of novel S. splendens cultivars and investigating the relevant molecular mechanisms are of great significance. In this study, RNA-sequencing and real-time PCR methods were used to analyze the possible molecular mechanism of S. splendens mutant, SX919M. From the wild-type S. splendens 919CK, we firstly selected a natural mutant, SX919M, which displayed multiple branches, clustered spheroids, and radial symmetrical inflorescence with higher numbers of calyces, ovules, stamens, and perianth tubes. Further, the RNA-seq was used to identify the differentially expressed genes (DEGs) in the mutant which included a total of 3568 upregulated and 3290 downregulated unigenes. We further observed that the indole alkaloid biosynthesis pathway showed the highest DEG enrichment, which was supported by a significant increase in the IAA content in mutant SX919M. In addition, we validated three DEGs, namely, CL2200.Contig2_All encoding methyl IAA esterase, CL12462.Contig1_All and CL12462.Contig2_All, which encoded strictosidine synthase, upregulated in mutant SX919M. We selected a novel S. splendens germplasm SX919M with a high ornamental value and determined that the upregulation of IAA biogenesis may be associated with its development.

A new and unusual endemic species from the Chihuahuan Desert, Mexico: Antiphytum geoffreyi (Boraginaceae, Echiochiloideae)

A new and unusual species of Antiphytum, here named A. geoffreyi, is described and illustrated. This new species is assigned to the genus Antiphytum because it possesses eremocarps directly attached to a pyramidal gynobase, which forms a ventral cicatrix on the eremocarp. However, it is unique within Antiphytum in having multiple inflorescence branches arising nearly at the base of the plant, a triangular-pyramidal gynobase, and the proportionally longest eremocarp cicatrix of the genus. Some of these characteristics are reminiscent of Ogastemma, the sister genus of Antiphytum, making A. geoffreyi of potential great significance in the systematics of Boraginaceae subfam. Echiochiloideae. Among species of Antiphytum, A. geoffreyi is most similar to A. peninsulare, with which it shares a triangular-shaped eremocarp, but it differs from this species in possessing an infra-medial cicatrix and a smaller corolla limb diameter. The new species is known from only two collections in Coahuila, Mexico, both made by the Hinton family, who have discovered many new species in their extensive explorations of the country and provided important specimens to the country’s flora.

Taxonomic notes on ornamental bananas in Thailand

More than 18 wild banana (Musaceae) species and hundreds of cultivars were found in Thailand, many are introduced as ornamentals. The banana family which is classified into three genera: Musa, Ensete and Musella, distributes in the old world tropics and Thailand is among their centers of origin. Many banana species possess attractive bract colors such as orange, pink, bright red, purple, and also, though less frequently found, yellow and green. Several other appealing features of the bananas are dwarf pseudostems, variegated leaves, multiple male inflorescence, uneven colored inflorescence bracts and numerous hands of fruits. Recently, three new banana species, Musa siamensis Hakkinen & Rich. H. Wallace, M. serpentina Swangpol & Somana and M. nanensis Swangpol & Traiperm were discovered in the country. These bananas have decorative potential; taxonomic revision could enhance the selection process of these taxa and bring them into the spot light as economic ornamental crops.

Euscelis incisus(Cicadellidae, Deltocephalinae), a natural vector of 16SrIII-B phytoplasma causing multiple inflorescence disease ofCirsium arvense

We investigated multiple inflorescence disease of Cirsium arvense (CMI) and its association with phytoplasmas of the 16SrIII-B subgroup, potential natural vector(s) and reservoir plant(s). From five locations in northern Serbia, 27 plants of C. arvense, 1 C. vulgare and 3 Carduus acanthoides with symptoms of multiple inflorescences (MIs) were collected and tested for 16SrIII group phytoplasmas. All symptomatic plants were found to be infected. Tentative reservoir plants and insect vectors were collected at a Dobanovci site where the continuous presence of CMI disease was recorded. Among the 19 most abundant plant species submitted to phytoplasma testing, all symptomless, the presence of the 16SrIII group was detected only in two legumes: Lathyrus tuberosus (2/5) and L. aphaca (1/5). Among 19 insect species from six families of Auchenorrhyncha, the deltocephalid leafhopper Euscelis incisus was the only insect carrying a 16SrIII phytoplasma (10% of analysed individuals). Transmission trials were performed with naturally infected E. incisus adults of the summer generation and with a laboratory population reared on red clover. After an acquisition period of 48 h on C. arvense symptomatic for MIs and a latent period of 28 days, 83% of the E. incisus adults (300/360) were infected with CMI phytoplasma. In two transmission tests, the leafhoppers successfully transmitted the phytoplasma to exposed plants (C. arvense and periwinkle), proving its role as a natural vector. Test plants of C. arvense infected with the 16SrIII-B phytoplasma expressed typical symptoms similar to those observed in the field, such as MIs or the absence of flowering, shortened internodes and plant desiccation. Typical symptoms in infected periwinkles were virescence and phyllody. The molecular characterisation of the CMI phytoplasma isolates from diseased and asymptomatic field-collected plants, vectors, and test plants was performed by sequence analyses of the 16S rRNA, rpl22-rps3 and rpl15-secY genes. Phylogenetic analyses of other members of the 16SrIII group of phytoplasmas indicated closest relatedness with clover yellow edge phytoplasma (CYE) of the 16SrIII-B subgroup.

Multiple Arrowing: A Rare Phenomenon in a Related Wild Species of Sugarcane

Sugarcane belongs to the family Poaceae (Gramineae) and its inflorescence is a panicle called as arrow. In general each flowering stalk terminates into single arrow. In EA Bethuadahari, a clone belongs to Erianthus arundinaceus produced multiple inflorescence from each stalk. Up to four inflorescences in each stalk with varying length was observed. Slight variation in pollen fertility was also recorded. Although it has less significance for commercial exploitation, its importance in crossing programme, genetical studies and implication of genes controlling multiple inflorescence in other Gramineae species are discussed.

The Arabidopsis Rho of Plants GTPase AtROP6 Functions in Developmental and Pathogen Response Pathways

How plants coordinate developmental processes and environmental stress responses is a pressing question. Here, we show that Arabidopsis (Arabidopsis thaliana) Rho of Plants6 (AtROP6) integrates developmental and pathogen response signaling. AtROP6 expression is induced by auxin and detected in the root meristem, lateral root initials, and leaf hydathodes. Plants expressing a dominant negative AtROP6 (rop6(DN)) under the regulation of its endogenous promoter are small and have multiple inflorescence stems, twisted leaves, deformed leaf epidermis pavement cells, and differentially organized cytoskeleton. Microarray analyses of rop6(DN) plants revealed that major changes in gene expression are associated with constitutive salicylic acid (SA)-mediated defense responses. In agreement, their free and total SA levels resembled those of wild-type plants inoculated with a virulent powdery mildew pathogen. The constitutive SA-associated response in rop6(DN) was suppressed in mutant backgrounds defective in SA signaling (nonexpresser of PR genes1 [npr1]) or biosynthesis (salicylic acid induction deficient2 [sid2]). However, the rop6(DN) npr1 and rop6(DN) sid2 double mutants retained the aberrant developmental phenotypes, indicating that the constitutive SA response can be uncoupled from ROP function(s) in development. rop6(DN) plants exhibited enhanced preinvasive defense responses to a host-adapted virulent powdery mildew fungus but were impaired in preinvasive defenses upon inoculation with a nonadapted powdery mildew. The host-adapted powdery mildew had a reduced reproductive fitness on rop6(DN) plants, which was retained in mutant backgrounds defective in SA biosynthesis or signaling. Our findings indicate that both the morphological aberrations and altered sensitivity to powdery mildews of rop6(DN) plants result from perturbations that are independent from the SA-associated response. These perturbations uncouple SA-dependent defense signaling from disease resistance execution.

Taxonomic status of three taxa of Elsholtzia (E. hallasanensis, E. springia, and E. splendens var. fasciflora) (Lamiaceae) based on molecular data

Elsholtzia hallasanensis, E. springia, and E. splendens var. fasciflora (Lamiaceae) were reported recently as new species or new varieties of E. splendens according to their morphological characteristics. To reappraise the taxonomic status of these additional taxa and to determine the relationships between all Korean Elsholtzia taxa except E. saxatilis, which is distributed in North Korea, molecular studies based on the nrDNA (ITS) and cpDNA (rpl16, and trnH-psbA) sequences of seven taxa of Elsholtzia and one outgroup were carried out. The molecular data support that E. angustifolia and E. minima are distinct species from E. splendens and E. ciliata, respectively, because they have several private marker genes and show monophyly. The molecular data also support that E. splendens has a very close taxonomic relationship with both E. hallasanensis and E. springia. We found that E. splendens var. fasciflora, with multiple inflorescence, was based on several private marker genes and on the monophyly of its trees, suggesting that it can be considered as a variety. Elsholtzia springia, with the same sequences and the same morphological characteristics with E. hallasanensis after transplanting, should be treated as a synonym of E. hallasanensis. Moreover, we consider the taxonomic status of E. hallasanensis as E. splendens var. hallasanensis (Y. Lee) N.S. Lee & C.S. Lee, stat. nov.

A test of the effect of floral color change on pollination effectiveness using artificial inflorescences visited by bumblebees

Floral color change has been recognized as a pollination strategy, but its relative effectiveness has been evaluated insufficiently with respect to other floral traits. In this study, effects of floral color change on the visitation pattern of bumblebees were empirically assessed using artificial flowers. Four inflorescence types were postulated as strategies of flowering behavior: type 1 has no retention of old flowers, resulting in a small display size; type 2 retains old flowers without nectar production; type 3 retains old flowers with nectar; and type 4 retains color-changed old flowers without nectar. Effects of these treatments varied depending on both the total display size (single versus multiple inflorescences) and the pattern of flower-opening. In the single inflorescence experiment, a large floral display due to the retention of old flowers (types 2-4) enhanced pollinator attraction, and the number of flower visits per stay decreased with color change (type 4), suggesting a decrease in geitonogamous pollination. Type-4 plants also reduced the foraging time of bees in comparison with type-2 plants. In the multiple inflorescence experiment, the retention of old flowers did not contribute to pollinator attraction. When flowering occurred sequentially within inflorescences, type-4 plants successfully decreased the number of visits and the foraging time in comparison with type-2 plants. In contrast, floral color change did not influence the number of visits, and it extended the foraging time when flowering occurred simultaneously within inflorescences but the opening of inflorescences progressed sequentially within a plant. Therefore, the effectiveness of floral color change is highly susceptible to the display size and flowering pattern within plants, and this may limit the versatility of the color change strategy in nature.

Floral displays: genetic control of grass inflorescences

Inflorescences in angiosperms are complex structures that have many different types of meristems. Among complex inflorescences, the best studied are in the grass family. Multiple inflorescence genes have been cloned from grasses over the past few years, many of them by positional cloning using the rice genome as a source of positional information. Several genes affect the apical meristem of the inflorescence differently from the lateral branch meristems, allowing morphological differentiation that permits diversification. ramosa1 (ra1), ra2, and ra3 have been cloned from maize and form part of a network of genes that control the production of lateral branching. Curiously, only ra2 is widely conserved; to date, ra1 and ra3 have been found only in Andropogoneae. Additional domestication genes that affect the inflorescence have also been cloned from maize, rice, and wheat.

First report of multiple inflorescence disease of Cirsium arvense and its association with a 16SrIII‐B subgroup phytoplasma in Serbia

Multiple inflorescences on Cirsium arvense (Asteraceae) have always been attributed to the presence of eriophyid mites, since their first record in 1892 (Petanovićet al., 1997). Plants showing symptoms of varying intensity were recorded from more than 10 sites in northern Serbia between 2001 and 2003. Affected plants showed irregular growth, atypical branching with small leaves, shortened internodes, hardening of the green inflorescence and reduced vigour, as well as either chlorosis or reddish-brown discoloration of the leaves and stems. Plants that reached flowering sometimes had multiple inflorescences. In the field the disease persists for years, increasing slowly around the original infection focus. Infected plants senesce prematurely, inhibiting both seed production and rhizome propagation, which markedly reduces the C. arvense population. DNA was extracted from eight samples of fresh leaf midribs and multiple inflorescences from affected plants, and from similar tissues of four plants without symptoms. This DNA was used as template in a nested PCR using universal phytoplasma primers P1/P7, followed by primers F1/B6 (band 1700 bp) and then primers R16F2/R2 (Duduk et al., 2004). Subsequent RFLP analyses with HpaII, TruI and HhaI restriction endonucleases were carried out. All samples from plants with symptoms were PCR positive, while those from the four symptomless plants were negative. RFLP patterns from the R16F2/R2 amplicons were identical to those of clover yellow edge phytoplasma (subgroup 16SrIII-B) but different from the TruI and HpaII profiles obtained using a reference strain of peach X disease. These results were confirmed using primers R16(III)F2/R1, which are specific for group 16SrIII phytoplasmas and which amplify an ≈800 bp product (Lee et al., 1994). This is the first report of multiple inflorescence disease of Cirsium in Serbia and of its association with phytoplasmas belonging to rRNA group 16SrIII-B. These phytoplasmas have recently been identified in plants with similar symptoms in Hungarian vineyards (Palermo et al., 2004) and in other herbaceous or woody host species.