CUC1 and CUC2 regulate ovule and seed number by modulating the expression of genes involved in the balance between active and inactive forms of glycosylated cytokinin.
Abstract
Seeds derive from ...ovules upon fertilization and therefore the total number of ovules determines the final seed yield, a fundamental trait in crop plants. Among the factors that co-ordinate the process of ovule formation, the transcription factors CUP-SHAPED COTYLEDON 1 (CUC1) and CUC2 and the hormone cytokinin (CK) have a particularly prominent role. Indeed, the absence of both CUC1 and CUC2 causes a severe reduction in ovule number, a phenotype that can be rescued by CK treatment. In this study, we combined CK quantification with an integrative genome-wide target identification approach to select Arabidopsis genes regulated by CUCs that are also involved in CK metabolism. We focused our attention on the functional characterization of UDP-GLUCOSYL TRANSFERASE 85A3 (UGT85A3) and UGT73C1, which are up-regulated in the absence of CUC1 and CUC2 and encode enzymes able to catalyse CK inactivation by O-glucosylation. Our results demonstrate a role for these UGTs as a link between CUCs and CK homeostasis, and highlight the importance of CUCs and CKs in the determination of seed yield.
Strategic Control in a Naming Task Lupker, Stephen J; Brown, Patrick; Colombo, Lucia
Journal of experimental psychology. Learning, memory, and cognition,
05/1997, Letnik:
23, Številka:
3
Journal Article
Recenzirano
S. Monsell, K. E. Patterson, A. Graham, C. H. Hughes, and
R. Milroy (1992)
reported that high-frequency irregular words are named faster when presented in a "pure" block than when mixed with ...nonwords. They attributed this effect to a de-emphasis of an assembly route in the pure block. The current authors replicated this effect in Experiment 1. In Experiments 2 and 3, similar effects resulted from mixing high- and low-frequency regular words with nonwords and from mixing high- and low-frequency irregular words together. Further, in all cases, the more slowly named stimuli were named faster in mixed blocks than in pure blocks. An alternative to the de-emphasis account, which is based on strategic control of initiation of articulation, was supported in Experiment 4 by confirming the alternative account's novel prediction of a regularity effect for high-frequency words in pure blocks. Implications for the single- versus dual-route debate and for interpretations of strategy effects in general are discussed.
•What is the developmental trend of transposed letter effects?•Three groups of children and adults were tested in lexical decision with masked priming on Italian words.•Pries included transposed and ...replaced letters of Italian words.•Facilitation of transposed letters primes compared to replaced letters primes increased with age.•Whether there is an increasing or decreasing trend depends on the transparency of the language.
In the current study, we investigated the development of transposed letter (TL) priming effects with masked priming. Recent studies have reported different and contrasting results concerning the age at which TL priming effects first appear and whether they tend to decline or increase with age. One of the aims of this study was to investigate the developmental trend of orthographic mechanisms underlying the TL effects in Italian. We tested three groups of children (second, third, and fifth graders) and a group of adults with a sandwich masked priming procedure, presenting lists of target words preceded by TL or replaced letter (RL) primes. TLs and RLs were either at the beginning (second–third letters) or the end (fourth–sixth letters) of primes in order to see whether the TL priming effect varied according to position in the letter string. We found that TL priming effects increased with age in both accuracy and latency. No effect of position was found. The results are discussed in light of a possible difference in the development of orthographic mechanisms depending on the transparency of the language.
We examined the development of stress assignment in reading Italian aloud. We investigated frequency effects as a marker of the use of item-specific lexical knowledge in assigning stress together ...with stress dominance and stress neighbourhood (the number of words sharing both stress and ending) as markers of distributional information regarding properties of the lexicon extracted from spoken language. We tested second- and fourth-graders in a reading-aloud experiment including high- and low-frequency words and nonwords. Results show that despite the regularity of orthography-phonology mappings in Italian and the predominant use of phonological recoding procedures, item-specific lexical knowledge is also used, even by beginning readers. The frequency effect was significant and did not increase with age, while stress errors on low-frequency words decreased with increasing grade. Stress neighbourhood increasingly affected stress assignment on nonwords with older children. Taken together, our findings show that both item-specific knowledge and general information about stress distribution are relevant in children's reading, suggesting the simultaneous use of both lexical and sublexical information. Moreover, as the reading system develops, and knowledge about the relative distribution of stress neighbourhood increases, larger grain-size units are also exploited.
We investigated production of lexical stress in children with and without autism spectrum disorders (ASD), all monolingual Italian speakers. The mean age of the 16 autistic children was 5.73 years ...and the mean age of the 16 typically developing children was 4.65 years. Picture-naming targets were five trisyllabic words that began with a weak–strong pattern of lexical stress across the initial two syllables (WS: matita) and five trisyllabic words beginning with a strong–weak pattern (SW: gomito). Acoustic measures of the duration, fundamental frequency, and intensity of the first two vowels for correct word productions were used to calculate a normalised Pairwise Variability Index (PVI) for WS and SW words. Results of acoustic analyses indicated no statistically significant group differences in PVIs. Results should be interpreted in line with the exploratory nature of this study. We hope this study will encourage additional cross-linguistic studies of prosody in children's speech production.
MADS-box proteins are transcription factors present in different eukaryotic kingdoms. In contrast to plants, for mammalian and yeast MADS-box proteins ternary complex formation with unrelated ...transcription factors was reported. We show here the first identification of such ternary interaction in plants. A rice seed-specific NF-YB was identified as partner of OsMADS18 by two-hybrid screening. NF-YB contains a histone fold motif, HFM,1 and is part of the trimeric CCAAT-binding NF-Y complex. OsMADS18, alone or in combination with a natural partner, interacts with OsNF-YB1 through the MADS and I regions. The mouse NF-YB also associates with OsMADS18in vivo and in vitro as a NF-YB-NF-YC dimer. Other rice MADS-box proteins do not interact in these assays, indicating specificity for the interaction. OsNF-YB1 is capable of heterodimerizing with NF-YC, but not trimerizing with NF-YA, thus precluding CCAAT binding. Mutation of the variant Asp at position 99 of the HFM α2-helix into a conserved serine recovers the capacity to interact with NF-YA, but not with DNA. This is the first indication that members of the NF-YB family work through mechanisms independent of the CCAAT box.
AINTEGUMENTA
(
ANT
) promotes initiation and growth of ovule integuments which cell fate is specified by ovule identity factors, such as
SEEDSTICK
(
STK
),
SHATTERPROOF1
(
SHP1
) and
SHATTERPROOF2
(
...SHP2
). To study the genetic interaction between
ANT
and the ovule identity genes, we have obtained a
stk shp1 shp2 ant
quadruple mutant. The molecular and morphological characterization of the quadruple mutant and its comparison with the
stk shp1 shp2
triple mutant, the
shp1 shp2 ant
triple mutant and the
stk ant
double mutant are here presented.
Angiosperms form the largest group of land plants and display an astonishing diversity of floral structures. The development of flowers greatly contributed to the evolutionary success of the ...angiosperms as they guarantee efficient reproduction with the help of either biotic or abiotic vectors. The female reproductive part of the flower is the gynoecium (also called pistil). Ovules arise from meristematic tissue within the gynoecium. Upon fertilization, these ovules develop into seeds while the gynoecium turns into a fruit. Gene regulatory networks involving transcription factors and hormonal communication regulate ovule primordium initiation, spacing on the placenta, and development. Ovule number and gynoecium size are usually correlated and several genetic factors that impact these traits have been identified. Understanding and fine-tuning the gene regulatory networks influencing ovule number and pistil length open up strategies for crop yield improvement, which is pivotal in light of a rapidly growing world population. In this review, we present an overview of the current knowledge of the genes and hormones involved in determining ovule number and gynoecium size. We propose a model for the gene regulatory network that guides the developmental processes that determine seed yield.
Abstract
Background and aims
The MBW complex consist of proteins belonging to three major families (MYB, bHLH and WDR) involved in various processes throughout plant development: epidermal cell ...development, mucilage secretory cells and flavonoid biosynthesis. Recently, it has been reported that TT8, encoding a bHLH transcription factor, is involved in the biosynthesis of flavonoids in the seed coat and it also plays a role in bypassing the postzygotic barrier resulting from an unbalance in genetic loads of the parental lines. Here, we focus on the functional evolution, in seed development, of the bHLH proteins that are part of the MBW complex, complemented with a literature review.
Methods
Phylogenetic analyses performed across seed plants and expression analyses in the reproductive tissues of four selected angiosperms (Arabidopsis thaliana, Brassica napus, Capsella rubella and Solanum lycopersicum) allow us to hypothesize on the evolution of its functions.
Key Results
TT8 expression in the innermost layer of the seed coat is conserved in the selected angiosperms. However, except for Arabidopsis, TT8 is also expressed in ovules, carpels and fruits. The homologues belonging to the sister clade of TT8, EGL3/GL3, involved in trichome development, are expressed in the outermost layer of the seed coat, suggesting potential roles in mucilage.
Conclusions
The ancestral function of these genes appears to be flavonoid biosynthesis, and the conservation of TT8 expression patterns in the innermost layer of the seed coat in angiosperms suggests that their function in postzygotic barriers might also be conserved. Moreover, the literature review and the results of the present study suggest a sophisticated association, linking the mechanisms of action of these genes to the cross-communication activity between the different tissues of the seed. Thus, it provides avenues to study the mechanisms of action of TT8 in the postzygotic triploid block, which is crucial because it impacts seed development in unbalanced crosses.
Apomixis is considered a potentially revolutionary tool to generate high-quality food at a lower cost and shorter developmental time due to clonal seed production through apomeiosis and ...parthenogenesis. In the diplosporous type of apomixis, meiotic recombination and reduction are circumvented either by avoiding or failing meiosis or by a mitotic-like division. Here, we review the literature on diplospory, from early cytological studies dating back to the late 19th century to recent genetic findings. We discuss diplosporous developmental mechanisms, including their inheritance. Furthermore, we compare the strategies adopted to isolate the genes controlling diplospory with those to produce mutants forming unreduced gametes. Nowadays, the dramatically improved technologies of long-read sequencing and targeted CRISPR/Cas mutagenesis justify the expectation that natural diplospory genes will soon be identified. Their identification will answer questions such as how the apomictic phenotype can be superimposed upon the sexual pathway and how diplospory genes have evolved. This knowledge will contribute to the application of apomixis in agriculture.
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