Organelle Ca2+/CAM1-SELTP confers somatic cell embryogenic competence acquisition and transformation in plant regeneration.

Somatic cell totipotency in plant regeneration represents the forefront of the compelling scientific puzzles and one of the most challenging problems in biology. How somatic embryogenic competence is achieved in regeneration remains elusive. Here, we discover uncharacterized organelle-based embryogenic differentiation processes of intracellular acquisition and intercellular transformation, and demonstrate the underlying regulatory system of somatic embryogenesis-associated lipid transfer protein (SELTP) and its interactor calmodulin1 (CAM1) in cotton as the pioneer crop for biotechnology application. The synergistic CAM1 and SELTP exhibit consistent dynamical amyloplast-plasmodesmata (PD) localization patterns but show opposite functional effects. CAM1 inhibits the effect of SELTP to regulate embryogenic differentiation for plant regeneration. It is noteworthy that callus grafting assay reflects intercellular trafficking of CAM1 through PD for embryogenic transformation. This work originally provides insight into the mechanisms responsible for embryogenic competence acquisition and transformation mediated by the Ca2+/CAM1-SELTP regulatory pathway, suggesting a principle for plant regeneration and cell/genetic engineering.

Haploid Bio-Induction in Plant through Mock Sexual Reproduction.

Haploidization is invaluable for basic genetic research and crop breeding. The haploid bio-induction principle is an important topic that remains largely unexplored. In this study, both CenH3 RNAi and in vitro inhibition were used to simulate and induce haploids in allopolyploid crop. Notably, in vitro CenH3 inhibition showed that the results were much the same to that of RNAi in phenotype, chromosome behavior, microspore production, and haploid induction. Cytological analyses of RNAi and inhibitor-treated progenies revealed elimination of chromosomes, defective microspores with empty nuclei, thereby giving rise to pseudo male gametes, and haploid parthenogenesis induction. We found distinct defective empty microspores that were positively correlated with the decrease of CenH3 during RNAi manipulation. Investigation through both in vivo and in vitro studies revealed that haploidization was induced through the pseudo male gamete-mediated mock sexual reproduction. The present results provide insights for the haploid parthenogenesis induction process.

Ectopic Expressions of the GhLETM1 Gene Reveal Sensitive Dose Effects on Precise Stamen Development and Male Fertility in Cotton.

The homologous leucine zipper/EF-hand-containing transmembranes (LETMs) are highly conserved across a broad range of eukaryotic organisms. The LETM functional characteristics involved in biological process have been identified primarily in animals, but little is known about the LETM biological function mode in plants. Based on the results of the current investigation, the GhLETM1 gene crucially affects filament elongation and anther dehiscence of the stamen in cotton. Both excessive and lower expression of the GhLETM1 gene lead to defective stamen development, resulting in shortened filaments and indehiscent anthers with pollen abortion. The results also showed that the phenotype of the shortened filaments was negatively correlated with anther defects in the seesaw model under the ectopic expression of GhLETM1. Moreover, our results notably indicated that the gene requires accurate expression and exhibits a sensitive dose effect for its proper function. This report has important fundamental and practical significance in crop science, and has crucial prospects for genetic engineering of new cytoplasmic male sterility lines and breeding of crop hybrid varieties.

Ethyl methanesulfonate mutant library construction in Gossypium hirsutum L. for allotetraploid functional genomics and germplasm innovation.

As the gene pool is exposed to both strain on land resources and a lack of diversity in elite allotetraploid cotton, the acquisition and identification of novel alleles has taken on epic importance in facilitating cotton genetic improvement and functional genomics research. Ethyl methanesulfonate (EMS) is an excellent mutagen that induces genome-wide efficient mutations to activate the mutagenic potential of plants with many advantages. The present study established, determined and verified the experimental procedure suitable for EMS-based mutant library construction as the general reference guide in allotetraploid upland cotton. This optimized method and procedure are efficient, and abundant EMS mutant libraries (approximately 12 000) in allotetraploid cotton were successfully obtained. More than 20 mutant phenotypes were observed and screened, including phenotypes of the leaf, flower, fruit, fiber and plant architecture. Through the plants mutant library, high-throughput and high-resolution melting technology-based variation evaluation detected the EMS-induced site mutation. Additionally, based on overall genome-wide mutation analyses by re-sequencing and mutant library assessment, the examination results demonstrated the ideal quality of the cotton EMS-treated mutant library constructed in this study with appropriate high mutation density and saturated genome. What is more, the collection is composed of a broad repertoire of mutants, which is the valuable resource for basic genetic research and functional genomics underlying complex allotetraploid traits, as well as cotton breeding.

Arbuscular mycorrhizal fungi (AMF) enhanced the growth, yield, fiber quality and phosphorus regulation in upland cotton (Gossypium hirsutum L.).

We previously reported on the strong symbiosis of AMF species (Rhizophagus irregularis CD1) with the cotton (Gossypium hirsutum L.) which is grown worldwide. In current study, it was thus investigated in farmland to determine the biological control effect of AMF on phosphorus acquisition and related gene expression regulation, plant growth and development, and a series of agronomic traits associated with yield and fiber quality in cotton. When AMF and cotton were symbiotic, the expression of the specific phosphate transporter family genes and P concentration in the cotton biomass were significantly enhanced. The photosynthesis, growth, boll number per plant and the maturity of the fiber were increased through the symbiosis between cotton and AMF. Statistical analysis showed a highly significant increase in yield for inoculated plots compared with that from the non inoculated controls, with an increase percentage of 28.54%. These findings clearly demonstrate here the benefits of AMF-based inoculation on phosphorus acquisition, growth, seed cotton yield and fiber quality in cotton. Further improvement of these beneficial inoculants on crops will help increase farmers' income all over the world both now and in the future.