Biochemical and Genetic Responses of Tea (Camellia sinensis (L.) Kuntze) Microplants under Mannitol-Induced Osmotic Stress In Vitro

Anabaena azollae - The cyanobacterial partner of Azolla filiculoides reciprocates variably to dose- and duration-dependent Bisphenol-A exposure

Bisphenol A (BPA) is one of the most studied endocrine-disrupting chemicals (EDC), for its large-scale production and disposal, and ubiquitous presence in the environment. It is also known to impart significant phytotoxic effects on almost all aquatic flora including cyanobacteria. Yet, there are limited studies on the responses of symbiotic cyanobacteria i.e. Anabaena azollae - residing inside Azolla filiculoides. In this context, this study aimed to investigate the response of A. azollae upon exposure to different doses and durations of BPA, which marks this as one of the first such studies. Morphological study reaffirmed the infiltration of BPA through the host's physical barrier and induced various anomalies like filament fragmentation, and cellular disruption especially heterocysts in the case of the higher doses of BPA (20, and 30 mg L-1). Additionally, exposure to higher doses further stimulated the antioxidative enzymes, secondary metabolites and stress/defence markers. However, the exaggerated ROS production (nearly 190%-230% O2.- and 557%-783% H2O2) at 30 mg L-1 severely disrupted the membrane integrity, osmotic balance, and reduced essential biomolecules like sugars, proteins and lipid accumulation. Moreover, higher doses of BPA treatment compromised photosynthetic activity by reducing the photosynthetic pigments and phycobiliproteins (PBPs). Conversely, up to the dose of 10 mg L-1, better cellular integrity, improved accumulation of biomolecules, pigments, and ROS detoxification denoted the neutral/positive effect on the symbionts. The lower doses (≥10 mg L-1) also showed positive indications like higher accumulation of biomolecules proteins (16%-30%), lipids (9%-49%), sugar (18%-52%), and pigments like phycobiliproteins (6%-97%), phycocyanins (6%-134%), which seemed to support the biomass of cyanobionts. Moreover, the said doses stimulated the accumulation of phenolics (98%-117%), flavonoids (159%-224%), and released polysaccharides (60%-183%) alongside stress markers like ascorbate and proline indicating the evocation of defense strategy against BPA stress.

Single-cell RNA-seq reveals a link of ovule abortion and sugar transport in Camellia oleifera

Camellia oleifera is the most important woody oil crop in China. Seed number per fruit is an important yield trait in C. oleifera. Ovule abortion is generally observed in C. oleifera and significantly decreases the seed number per fruit. However, the mechanisms of ovule abortion remain poorly understood at present. Single-cell RNA sequencing (scRNA-seq) was performed using mature ovaries of two C. oleifera varieties with different ovule abortion rates (OARs). In total, 20,526 high-quality cells were obtained, and 18 putative cell clusters were identified. Six cell types including female gametophyte, protoxylem, protophloem, procambium, epidermis, and parenchyma cells were identified from three main tissue types of ovule, placenta, and pericarp inner layer. A comparative analysis on scRNA-seq data between high- and low-OAR varieties demonstrated that the overall expression of CoSWEET and CoCWINV in procambium cells, and CoSTP in the integument was significantly upregulated in the low-OAR variety. Both the infertile ovule before pollination and the abortion ovule producing after compatible pollination might be attributed to selective abortion caused by low sugar levels in the apoplast around procambium cells and a low capability of hexose uptake in the integument. Here, the first single-cell transcriptional landscape is reported in woody crop ovaries. Our investigation demonstrates that ovule abortion may be related to sugar transport in placenta and ovules and sheds light on further deciphering the mechanism of regulating sugar transport and the improvement of seed yield in C. oleifera.

Tissue Culture—A Sustainable Approach to Explore Plant Stresses

Plants are constantly faced with biotic or abiotic stress, which affects their growth and development. Yield reduction due to biotic and abiotic stresses on economically important crop species causes substantial economic loss at a global level. Breeding for stress tolerance to create elite and superior genotypes has been a common practice for many decades, and plant tissue culture can be an efficient and cost-effective method. Tissue culture is a valuable tool to develop stress tolerance, screen stress tolerance, and elucidate physiological and biochemical changes during stress. In vitro selection carried out under controlled environment conditions in confined spaces is highly effective and cheaper to maintain. This review emphasizes the relevance of plant tissue culture for screening major abiotic stresses, drought, and salinity, and the development of disease resistance. Further emphasis is given to screening metal hyperaccumulators and transgenic technological applications for stress tolerance.