Morphological, Physiological and Biochemical Response to Low Temperature Stress in Tomato (Solanum lycopersicum L.): A Review

Growth and productivity are traumatized by the low temperature that triggers a series of physiological, morphological, molecular and biochemical changes in plants that eventually disturb plant life. Most of the cultivable lands of the world are adversely affected by temperature stress conditions which have an adverse impact on global tomato productivity. Plants undergo several water related metabolic activities for their survival during cold stress conditions. Understanding the morphological, physiological and biochemical reactions to low temperature is essential for a comprehensive view of the perception of tomato plant tolerant mechanism. This review reports some aspects of low temperature inflated changes in physiological and biochemical in the tomato plant. Low temperature stress influences the reproductive phases of plants with delayed flowering which enhance pollen sterility resultant drastically affects the harvest yield. It also decreases the capacity and efficiency of photosynthesis through changes in gas exchange, pigment content, chloroplast development and decline in chlorophyll fluorescence photosynthetic attributes. Amassing of osmoprotectant is another adaptive mechanism in plants exposed to low temperatures stress, as essential metabolites directly participate in the osmotic adjustment. Furthermore, low temperature stress enhanced the production of reactive oxygen species (ROS) which may oxidize lipids, proteins and nucleic acids which bring in distortion at the level of the cell. At the point when extreme reactive oxygen species produced, plants synthesize antioxidant enzymes and osmoprotectants that quench the abundance of reactive oxygen species. These reviews focus on the capacity and techniques of the tomato plant to react low temperature stress.

Inter-varietal sterility and fertility restoration in Oryza sativa Linn.

This study explored the underlining reproductive factors that cause sterility in rice, using hybrids obtained from crosses among landrace selections and improved varieties. The study was carried out between 2016 and 2018. Nine landrace cultivars and two improved varieties were involved in the hybridization experiment. Among the 17 putative hybrids that were obtained, only 5 were confirmed as true hybrids. Meiotic chromosome studies and pollen studies in the F1, and Mendelian segregation studies for fertility in the F2 were carried out. Some F2 lines were monitored to F3 to ascertain the level of fixation of gene combinations for fertility. The results obtained from the chromosomal studies showed that phenomena such as laggards, precocious movements, formation of multivalents, and unequal segregation to the poles are associated with pollen sterility in all - 5 hybrids, at the F1 and F2 generations. The indehiscence of anthers contributed to infertility due to pollen shortage than the fertility of the pollens themselves. Even though in males, there is a preponderance of male sterility, female sterility is also a phenomenon that is possibly contributing to inter-varietal sterility. The segregational pattern of 13:3 was observed for fertility in the F2 which suggests the inhibition of fertility by a gene in the dominant state. There was the restoration of fertility in many of the lines advanced to the F3 to up to 93 % fertility. It was, therefore, concluded from the study that landraces of rice still hold the key for the rice crop improvement and should therefore be conserved.

Integrated Isoform Sequencing and Dynamic Transcriptome Analysis Reveals Diverse Transcripts Responsible for Low Temperature Stress at Anther Meiosis Stage in Rice

Low temperatures stress is one of the important factors limiting rice yield, especially during rice anther development, and can cause pollen sterility and decrease grain yield. In our study, low-temperature stress decreased pollen viability and spikelet fertility by affecting the sugar, nitrogen and amino acid contents of anthers. We performed RNA-seq and ISO-seq experiments to study the genome-wide transcript expression profiles in low-temperature anthers. A total of 4,859 differentially expressed transcripts were detected between the low-temperature and control groups. Gene ontology enrichment analysis revealed significant terms related to cold tolerance. Hexokinase and glutamate decarboxylase participating in starch and sucrose metabolism may play important roles in the response to cold stress. Using weighted gene co-expression network analysis, nine hub transcripts were found that could improve cold tolerance throughout the meiosis period of rice: Os02t0219000-01 (interferon-related developmental regulator protein), Os01t0218350-00 (tetratricopeptide repeat-containing thioredoxin), Os08t0197700-00 (luminal-binding protein 5), Os11t0200000-01 (histone deacetylase 19), Os03t0758700-01 (WD40 repeat domain-containing protein), Os06t0220500-01 (7-deoxyloganetin glucosyltransferase), Pacbio.T01382 (sucrose synthase 1), Os01t0172400-01 (phospholipase D alpha 1), and Os01t0261200-01 (NAC domain-containing protein 74). In the PPI network, the protein minichromosome maintenance 4 (MCM4) may play an important role in DNA replication induced by cold stress.

The radish Ogura fertility restorer impedes translation elongation along its cognate CMS-causing mRNA

The control of messenger RNA (mRNA) translation has been increasingly recognized as a key regulatory step for gene control, but clear examples in eukaryotes are still scarce. Nucleo-cytoplasmic male sterilities (CMS) represent ideal genetic models to dissect genetic interactions between the mitochondria and the nucleus in plants. This trait is determined by specific mitochondrial genes and is associated with a pollen sterility phenotype that can be suppressed by nuclear genes known as restorer-of-fertility (Rf). In this study, we focused on the Ogura CMS system in rapeseed and showed that reversion to male sterility by the PPR-B fertility restorer (also called Rfo) occurs through a specific translation inhibition of the mitochondria-encoded CMS-causing mRNA orf138. We also demonstrate that PPR-B binds within the coding sequence of orf138 and acts as a ribosome blocker to specifically impede translation elongation along the orf138 mRNA. Rfo is the first recognized fertility restorer shown to act this way. These observations will certainly facilitate the development of synthetic fertility restorers for CMS systems in which efficient natural Rfs are lacking.

Comparative analysis of the efficacy of selected gametocide agents in sorghum (Sorghum bicolor [L.] Moench)

A new generation of chemical hybridization agents (CHAs) or gametocides has shown potential to induce male sterility in predominantly self-fertilizing crops, including sorghum (Sorghum bicolor [L.] Moench). There is a lack of information on the relative efficacy of the various available CHAs for large-scale application in plant breeding programs. Therefore, the objective of the present study was to compare the relative effectiveness of three selected CHAs to induce male sterility in sorghum under a controlled environment for hybridization. Foliar applications of three CHAs and a control (ethrel, trifluoromethanesulfonamide [TFMSA], ethyl 4-fluorooxanilate [E4FO] and distilled water [control]) were tested using three grain sorghum genotypes (ICS-1, ICS-2 and ICS-3) in two seasons. The 24 treatment combinations consisting of 4 levels of CHAs, 3 sorghum varieties and two seasons were laid out using a randomized complete block design with three replications. Data on pollen sterility, pollen diameter, plant height, and panicle height were collected and analyzed. Results showed that the CHAs had significant (p<0.05) differences for efficacy of inducing male sterility in sorghum. Ethrel at a dose of 1 gl-1 induced the highest pollen sterility (98% in both seasons) but was highly phytotoxic with at least 60% mortality in the test population in both seasons, making it unsuitable for practical application. TFMSA (2 mg per plant) and E4FO (1 gl-1) d induced 93% male sterility with minimal phytotoxic effects (20 to 30%). Application of either TFMSA at 2mg per plant after flag leaf emergence or 1gl-1 of E4FO at panicle initiation can be used to successfully induce male sterility in sorghum under greenhouse conditions

Interaction of gibberellin and other hormones in almond anthers: phenotypic and physiological changes and transcriptomic reprogramming

Low temperature causes anther dysfunction, severe pollen sterility and, ultimately, major yield losses in crop plants. Previous studies have shown that the gibberellic acid (GA) metabolic pathway plays an important role in this process by regulating tapetum function and pollen development. However, the interaction mechanism of GA with other hormones mediating anther development is still unclear. Herein, we collected and analyzed almond (Amygdalus communis L.) anthers at the meiosis, tetrad, 1-nucleus, and mature 2-nucleus stages. The growth rate per 1000 anthers exhibited a significant positive correlation with the total bioactive GA compound content, and the levels of all bioactive GA compounds were highest in the 1-nucleus pollen stage. GA3 treatment experiments indicated that exogenous GA3 increased the levels of indole-3-acetic acid (IAA), trans-zeatin (tZ), and jasmonic acid (JA) and decreased the levels of salicylic acid (SA) and abscisic acid (ABA); moreover, GA3 improved pollen viability and quantities under cold conditions, whereas PP333 (paclobutrazol, an inhibitor of GA biosynthesis) was antagonistic with GA3 in controlling anther development. RNA-seq and qRT-PCR results showed that GA played an important role in anther development by regulating the expression of other phytohormone pathway genes, dehydration-responsive element-binding/C-repeat binding factor (DREB1/CBF)-mediated signaling genes, and anther development pathway genes. Our results reveal the novel finding that GA interacts with other hormones to balance anther development under normal- and low-temperature conditions in almond.