Morphological characterization and genetic analysis of tri-pistil trait, a precisely regulated pistil number mutation in bread wheat

Bread wheat (Triticum aestivum L.) is an important source of nutrients for humans. Therefore, improvement of its yields is essential to feed the increasing world population. The tri-pistil (TRP) trait in wheat has a high potential for increasing yields. We obtained a pure tri-pistil wheat line, 4045, and evaluated its morphological properties. The 4045 wheat line stably produced three independently inherited pistils, which led to 1-3 grains in each floret. Among the three pistils, two lately emerged pistils initiated at late anther primordia stage to early tetrads stage. Genetic analysis revealed that there were TRP penetrance variations among the 11 F1 populations of 4045. Fine mapping narrowed the single dominant TRP locus to a 97.3 kb region, containing two candidate genes, on the 2DL chromosome. However, further gene sequence, functional as well as comparative genomic analyses ruled out the only two candidate genes. Therefore, TRP is high-likely a unique gain-of-function mutation that does not exist in normal wheat genome. Transcriptome analysis of floral homeotic genes revealed that expressions of the C-class TaAG-2s, which are essential for carpel specification, significantly increased in 4045, implying that TaAG-2s have played important roles in TRP-regulated tri-pistil formation. This study highlights that TRP leads to a precisely regulated pistil number increase (PRPNI) mutations and proposed a regulatory model of PRPNI pistil architecture. PRPNI offers a novel abnormal pistil development resource for research of floral architectures and potential on crop yield improvement.

Gene regulation network analyses of pistil development in papaya

Background The pistil is an essential part of flowers that functions in the differentiation of the sexes and reproduction in plants. The stigma on the pistil can accept pollen to allow fertilization and seed development. Papaya (Carica papaya L.) is a dioecious plant, where female flowers exhibit normal pistil, while the male flowers exhibit aborted pistil at a late stage of pistil development. Results The developmental stages of papaya pistil were analyzed after first dividing it into slices representing the primordium stage 1 (S1), the pre-meiotic stages S2, post-meiotic stage S3, and the mitotic stage S4. The SS scoring algorithm analysis of genes preferentially expressed at different stages revealed differentially expressed genes between male and female flowers. A transcription factor regulatory network for each stage based on the genes that are differentially expressed between male and female flowers was constructed. Some transcription factors related to pistil development were revealed based on the analysis of regulatory networks such as CpAGL11, CpHEC2, and CpSUPL. Based on the specific expression of genes, constructed a gene regulatory subnetwork with CpAGL11-CpSUPL-CpHEC2 functioning as the core. Analysis of the functionally enriched terms in this network reveals several differentially expressed genes related to auxin/ brassinosteroid signal transduction in the plant hormone signal transduction pathway. At the same time, significant differences in the expression of auxin and brassinosteroid synthesis-related genes between male and female flowers at different developmental stages were detected. Conclusions The pistil abortion of papaya might be caused by the lack of expression or decreased expression of some transcription factors and hormone-related genes, affecting hormone signal transduction or hormone biosynthesis. Analysis of aborted and normally developing pistil in papaya provided new insights into the molecular mechanism of pistil development and sex differentiation in dioecious papaya.

IS THE FLOWER OF PULASAN (NEPHELIUM RAMBOUTAN-AKE) A PROTOGYNY OR PROTANDRY?

Pulasan is an androdioecious plant that has both male and hermaphrodite flowers on separate plants. The objectives of this study were to obtain data about the anatomical structure of pulasan flower and to investigate whether the pistil and the stamens of pulasan flower reach maturity at different times. The anatomical observation was done on compound flowers taken from three male trees and three hermaphrodite trees. Two compound flowers that still in buds, about to bloom and fully bloom were picked from each tree. Flowers were observed in a cross and longitudinal section. The results showed that the sepals of pulasan flower comprised of the uniseriate epidermis and multilayered polyhedral parenchymal cells. Stamen development started from the anther followed by the formation of the filament. The pollen of hermaphrodite pulasan flowers reached maturation earlier than the pistil. The pistil development started from the expansion of meristem cells in the center of the flower and ends with the warp of the stigma.

The SAP function in pistil development was proved by two allelic mutations in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Background Pistil development is a complicated process in plants, and female sterile mutants are ideal material for screening and cloning pistil development-related genes. Using the female sterile mutant (fsm1), BraA04g009730.3C was previously predicted as a candidate mutant gene encoding the STERILE APETALA (SAP) transcriptional regulator. In the current study, a parallel female sterile mutant (fsm2) was derived from EMS mutagenesis of a Chinese cabbage DH line ‘FT’ seeds. Results Both fsm2 and fsm1 mutant phenotypes exhibited pistil abortion and smaller floral organs. Genetic analysis indicated that the phenotype of mutant fsm2 was also controlled by a single recessive nuclear gene. Allelism testing showed that the mutated fsm1 and fsm2 genes were allelic. A single-nucleotide mutation (G-to-A) in the first exon of BraA04g009730.3C caused a missense mutation from GAA (glutamic acid) to GGA (glycine) in mutant fsm2 plants. Both allelic mutations of BraA04g009730.3C in fsm1 and fsm2 conferred the similar pistil abortion phenotype, which verified the SAP function in pistil development. To probe the mechanism of SAP-induced pistil abortion, we compared the mutant fsm1 and wild-type ‘FT’ pistil transcriptomes. Among the 3855 differentially expressed genes obtained, 29 were related to ovule development and 16 were related to organ size. Conclusion Our study clarified the function of BraA04g009730.3C and revealed that it was responsible for ovule development and organ size. These results lay a foundation to elucidate the molecular mechanism of pistil development in Chinese cabbage.

Genome-wide Identification and Functional Analysis of the H3 Gene Family in Cotton

Background: Histones are major components of chromatin, which is a nucleosome structure associated with chromosome segregation, DNA packaging and transcriptional regulation. Histone H3 is encoded by many genes in most eukaryotic species, but little information is known about the Histone H3 gene family in cotton.Results: In this study, we identified and analyzed the evolution and expression of histone H3 gene family in cotton. First, 34 G. hirsutum genes were identified belonging to the H3 gene family which were divided into four subclasses: CENH3, H3.1, H3.3 and H3-like. Among these H3.1 subclass contained the highest number of genes (22 members) followed by H3.3 subclass (9 members). In addition, there were18 and 16 H3 genes identified in G. arboretum and G. raimondii, respectively. Furthermore, we conducted conserved sequence analysis of H3 proteins, and found that the four amino acids signature including A31F41S87A90 for H3.1 and T31Y41H87L90 for H3.3 could be used to discriminate H3.1 from H3.3. The expression of H3 gene family varied in different tissues and developmental stages of G. hirsutum, where H3.1 subclass genes play a critical role in pistil development. By virus-induced gene silencing of GhCENH3 (Gh_D07G1382) gene, the size of leaf got smaller with pYL156-CENH3 than that with pYL156 in TM-1. Whereas, the number of the stomata in the leaf epidermis and number of chloroplasts in the leaf stomatal guard cells by pYL156-CENH3 was more than that by pYL156 and pYL156-PDS.Conclusions: Four sub-classes (CENH3, H3.1, H3.3 and H3-like) of H3 gene family were highly conserved in cotton during the rapid phase of evolution among which CENH3 is necessary for leaf growth. These findings are useful for providing further insights into cotton biology and breeding.

Transcriptomic analysis reveals ethylene signal transduction genes involved in pistil development of pumpkin

Development of female flowers is an important process that directly affects the yield of Cucubits. Little information is available on the sex determination and development of female flowers in pumpkin, a typical monoecious plant. In the present study, we used aborted and normal pistils of pumpkin for RNA-Seq analysis and determined the differentially expressed genes (DEGs) to gain insights into the molecular mechanism underlying pistil development in pumpkin. A total of 3,817 DEGs were identified, among which 1,341 were upregulated and 2,476 were downregulated. The results of transcriptome analysis were confirmed by real-time quantitative RT-PCR. KEGG enrichment analysis showed that the DEGs were significantly enriched in plant hormone signal transduction and phenylpropanoid biosynthesis pathway. Eighty-four DEGs were enriched in the plant hormone signal transduction pathway, which accounted for 12.54% of the significant DEGs, and most of them were annotated as predicted ethylene responsive or insensitive transcription factor genes. Furthermore, the expression levels of four ethylene signal transduction genes in different flower structures (female calyx, pistil, male calyx, stamen, leaf, and ovary) were investigated. The ethyleneresponsive DNA binding factor, ERDBF3, and ethylene responsive transcription factor, ERTF10, showed the highest expression in pistils and the lowest expression in stamens, and their expression levels were 78- and 162-times more than that in stamens, respectively. These results suggest that plant hormone signal transduction genes, especially ethylene signal transduction genes, play an important role in the development of pistils in pumpkin. Our study provides a theoretical basis for further understanding of the mechanism of regulation of ethylene signal transduction genes in pistil development and sex determination in pumpkin.