Giberellic Acid-Stimulated Transcript Proteins Evolved through Successive Conjugation of Novel Motifs and Their Subfunctionalization

A gibberellin-assisted study of the transcriptional and hormonal changes occurring at floral transition in peach buds (Prunus persica L. Batsch)

BACKGROUND

Flower load in peach is an important determinant of final fruit quality and is subjected to cost-effective agronomical practices, such as the thinning, to finely balance the sink-source relationships within the tree and drive the optimal amount of assimilates to the fruits. Floral transition in peach buds occurs as a result of the integration of specific environmental signals, such as light and temperature, into the endogenous pathways that induce the meristem to pass from vegetative to reproductive growth. The cross talk and integration of the different players, such as the genes and the hormones, are still partially unknown. In the present research, transcriptomics and hormone profiling were applied on bud samples at different developmental stages. A gibberellin treatment was used as a tool to identify the different phases of floral transition and characterize the bud sensitivity to gibberellins in terms of inhibition of floral transition.

RESULTS

Treatments with gibberellins showed different efficacies and pointed out a timeframe of maximum inhibition of floral transition in peach buds. Contextually, APETALA1 gene expression was shown to be a reliable marker of gibberellin efficacy in controlling this process. RNA-Seq transcriptomic analyses allowed to identify specific genes dealing with ROS, cell cycle, T6P, floral induction control and other processes, which are correlated with the bud sensitivity to gibberellins and possibly involved in bud development during its transition to the reproductive stage. Transcriptomic data integrated with the quantification of the main bioactive hormones in the bud allowed to identify the main hormonal regulators of floral transition in peach, with a pivotal role played by endogenous gibberellins and cytokinins.

CONCLUSIONS

The peach bud undergoes different levels of receptivity to gibberellin inhibition. The stage with maximum responsiveness corresponded to a transcriptional and hormonal crossroad, involving both flowering inhibitors and inductors. Endogenous gibberellin levels increased only at the latest developmental stage, when floral transition was already partially achieved, and the bud was less sensitive to exogenous treatments. A physiological model summarizes the main findings and suggests new research ideas to improve our knowledge about floral transition in peach.

Genome-Wide Identification and Characterization of Gibberellic Acid-Stimulated Arabidopsis Gene Family in Pineapple (Ananas comosus)

The gibberellic acid-stimulated Arabidopsis (GASA) gene family plays a crucial role in growth, development, and stress response, and it is specific to plants. This gene family has been extensively studied in various plant species, and its functional role in pineapple has yet to be characterized. In this study, 15 AcGASA genes were identified in pineapple through a genome-wide scan and categorized into three major branches based on a phylogenetic tree. All AcGASA proteins share a common structural domain with 12 cysteine residues, but they exhibit slight variations in their physicochemical properties and motif composition. Predictions regarding subcellular localization suggest that AcGASA proteins are present in the cell membrane, Golgi apparatus, nucleus, and cell wall. An analysis of gene synteny indicated that both tandem and segmental repeats have a significant impact on the expansion of the AcGASA gene family. Our findings demonstrate the differing regulatory effects of these hormones (GA, NAA, IAA, MeJA, and ABA) on the AcGASA genes. We analyzed the expression profiles of GASA genes in different pineapple tissue parts, and the results indicated that AcGASA genes exhibit diverse expression patterns during the development of different plant tissues, particularly in the regulation of floral organ development. This study provides a comprehensive understanding of GASA family genes in pineapple. It serves as a valuable reference for future studies on the functional characterization of GASA genes in other perennial herbaceous plants.

GASA Proteins: Review of Their Functions in Plant Environmental Stress Tolerance

Gibberellic acid-stimulated Arabidopsis (GASA) gene family is a class of functional cysteine-rich proteins characterized by an N-terminal signal peptide and a C-terminal-conserved GASA domain with 12 invariant cysteine (Cys) residues. GASA proteins are widely distributed among plant species, and the majority of them are involved in the signal transmission of plant hormones, the regulation of plant development and growth, and the responses to different environmental constraints. To date, their action mechanisms are not completely elucidated. This review reports an overview of the diversity, structure, and subcellular localization of GASA proteins, their involvement in hormone crosstalk and redox regulation during development, and plant responses to abiotic and biotic stresses. Knowledge of this complex regulation can be a contribution to promoting multiple abiotic stress tolerance with potential agricultural applications through the engineering of genes encoding GASA proteins and the production of transgenic plants.

Genome-Wide Identification and Functional Analysis of the GASA Gene Family Responding to Multiple Stressors in Canavalia rosea

In plants, the Gibberellic Acid-Stimulated Arabidopsis (GASA) gene family is unique and responds to ubiquitous stress and hormones, playing important regulatory roles in the growth and development of plants, as well as in the resistance mechanisms to biotic and abiotic stress. In this study, a total of 23 CrGASAs were characterized in C. rosea using a genome-wide approach, and their phylogenetic relationships, gene structures, conserved motifs, chromosomal locations, gene duplications, and promoter regions were systematically analyzed. Expression profile analysis derived from transcriptome data showed that CrGASAs are expressed at higher levels in the flowers or fruit than in the leaves, vines, and roots. The expression of CrGASAs also showed habitat- and environmental-stress-regulated patterns in C. rosea analyzed by transcriptome and quantitative reverse transcription PCR (qRT-PCR). The heterologous induced expression of some CrGASAs in yeast enhanced the tolerance to H2O2, and some CrGASAs showed elevated heat tolerance and heavy metal (HM) Cd/Cu tolerance. These findings will provide an important foundation to elucidate the biological functions of CrGASA genes, especially their role in the ecological adaptation of specific plant species to tropical islands and reefs in C. rosea.

Genome-Wide Identification, Evolution, and Expression Analysis of GASA Gene Family in Prunus mume

The Gibberellic Acid Stimulated Arabidopsis/Gibberellin Stimulated Transcript (GASA/GAST) gene family is a group of plant-specific genes encoding cysteine-rich peptides essential to plant growth, development, and stress responses. Although GASA family genes have been identified in various plant species, their functional roles in Prunus mume are still unknown. In this study, a total of 16 PmGASA genes were identified via a genome-wide scan in Prunus mume and were grouped into three major gene clades based on the phylogenetic tree. All PmGASA proteins possessed the conserved GASA domain, consisting of 12-cysteine residues, but varied slightly in protein physiochemical properties and motif composition. With evolutionary analysis, we observed that duplications and purifying selection are major forces driving PmGASA family gene evolution. By analyzing PmGASA promoters, we detected a number of hormonal-response related cis-elements and constructed a putative transcriptional regulatory network for PmGASAs. To further understand the functional role of PmGASA genes, we analyzed the expression patterns of PmGASAs across different organs and during various biological processes. The expression analysis revealed the functional implication of PmGASA gene members in gibberellic acid-, abscisic acid-, and auxin-signaling, and during the progression of floral bud break in P. mume. To summarize, these findings provide a comprehensive understanding of GASA family genes in P. mume and offer a theoretical basis for future research on the functional characterization of GASA genes in other woody perennials.

Genome-Wide Comprehensive Analysis of the GASA Gene Family in Populus

Gibberellic acid-stimulated Arabidopsis (GASA) proteins, as cysteine-rich peptides (CRPs), play roles in development and reproduction and biotic and abiotic stresses. Although the GASA gene family has been identified in plants, the knowledge about GASAs in Populus euphratica, the woody model plant for studying abiotic stress, remains limited. Here, we referenced the well-sequenced Populus trichocarpa genome, and identified the GASAs in the whole genome of P. euphratica and P. trichocarpa. 21 candidate genes in P. trichocarpa and 19 candidate genes in P. euphratica were identified and categorized into three subfamilies by phylogenetic analysis. Most GASAs with signal peptides were located extracellularly. The GASA genes in Populus have experienced multiple gene duplication events, especially in the subfamily A. The evolution of the subfamily A, with the largest number of members, can be attributed to whole-genome duplication (WGD) and tandem duplication (TD). Collinearity analysis showed that WGD genes played a leading role in the evolution of GASA genes subfamily B. The expression patterns of P. trichocarpa and P. euphratica were investigated using the PlantGenIE database and the real-time quantitative PCR (qRT-PCR), respectively. GASA genes in P. trichocarpa and P. euphratica were mainly expressed in young tissues and organs, and almost rarely expressed in mature leaves. GASA genes in P. euphratica leaves were also widely involved in hormone responses and drought stress responses. GUS activity assay showed that PeuGASA15 was widely present in various organs of the plant, especially in vascular bundles, and was induced by auxin and inhibited by mannitol dramatically. In summary, this present study provides a theoretical foundation for further research on the function of GASA genes in P. euphratica.

GhGASA10-1 promotes the cell elongation in fiber development through the phytohormones IAA-induced

BACKGROUND

Cotton is an important cash crop. The fiber length has always been a hot spot, but multi-factor control of fiber quality makes it complex to understand its genetic basis. Previous reports suggested that OsGASR9 promotes germination, width, and thickness by GAs in rice, while the overexpression of AtGASA10 leads to reduced silique length, which is likely to reduce cell wall expansion. Therefore, this study aimed to explore the function of GhGASA10 in cotton fibers development.

RESULTS

To explore the molecular mechanisms underlying fiber elongation regulation concerning GhGASA10-1, we revealed an evolutionary basis, gene structure, and expression. Our results emphasized the conservative nature of GASA family with its origin in lower fern plants S. moellendorffii. GhGASA10-1 was localized in the cell membrane, which may synthesize and transport secreted proteins to the cell wall. Besides, GhGASA10-1 promoted seedling germination and root extension in transgenic Arabidopsis, indicating that GhGASA10-1 promotes cell elongation. Interestingly, GhGASA10-1 was upregulated by IAA at fiber elongation stages.

CONCLUSION

We propose that GhGASA10-1 may promote fiber elongation by regulating the synthesis of cellulose induced by IAA, to lay the foundation for future research on the regulation networks of GASA10-1 in cotton fiber development.

Genetic and Molecular Factors Determining Grain Weight in Rice

Grain weight is one of the major factors determining single plant yield production of rice and other cereal crops. Research has begun to reveal the regulatory mechanisms underlying grain weight as well as grain size, highlighting the importance of this research for plant molecular biology. The developmental trait of grain weight is affected by multiple molecular and genetic aspects that lead to dynamic changes in cell division, expansion and differentiation. Additionally, several important biological pathways contribute to grain weight, such as ubiquitination, phytohormones, G-proteins, photosynthesis, epigenetic modifications and microRNAs. Our review integrates early and more recent findings, and provides future perspectives for how a more complete understanding of grain weight can optimize strategies for improving yield production. It is surprising that the acquired wealth of knowledge has not revealed more insights into the underlying molecular mechanisms. To accelerating molecular breeding of rice and other cereals is becoming an emergent and critical task for agronomists. Lastly, we highlighted the importance of leveraging gene editing technologies as well as structural studies for future rice breeding applications.

A quantitative trait locus GW6 controls rice grain size and yield through the gibberellin pathway

Grain size is one of the essential components determining rice yield and is a target for both domestication and artificial breeding. Gibberellins (GAs) are diterpenoid phytohormones that influence diverse aspects of plant growth and development. Several quantitative trait loci (QTLs) have been identified that control grain size through phytohormone regulation. However, little is known about the role of GAs in the control of grain size. Here we report the cloning and characterization of a QTL, GW6 (GRAIN WIDTH 6), which encodes a GA-regulated GAST family protein and positively regulates grain width and weight. GW6 is highly expressed in the young panicle and increases grain width by promoting cell expansion in the spikelet hull. Knockout of GW6 exhibits reduced grain size and weight, whereas overexpression of GW6 results in increased grain size and weight. GW6 is induced by GA and its knockout downregulates the expression of GA biosynthesis genes and decreases GA content in the young panicle. We found that a natural variation in the cis element CAAT-box in the promoter of GW6 is associated with its expression level and grain width and weight. Furthermore, introduction of GW6 to Oryza indica variety HJX74 can lead to a 10.44% increase in rice grain yield, indicating that GW6 has great potential to improve grain yield in rice.