The novel galactosyl transferase-like (SbGalT) gene from Salicornia brachiata maintains photosynthesis and enhances abiotic stress tolerance in transgenic tobacco

ZmASR1 negatively regulates drought stress tolerance in maize

Abscisic acid-, stress-, and ripening-induced (ASR) proteins in plants play a significant role in plant response to diverse abiotic stresses. However, the functions of ASR genes in maize remain unclear. In the present study, we identified a novel drought-induced ASR gene in maize (ZmASR1) and functionally characterized its role in mediating drought tolerance. The transcription of ZmASR1 was upregulated under drought stress and abscisic acid (ABA) treatment, and the ZmASR1 protein was observed to exhibit nuclear and cytoplasmic localization. Moreover, ZmASR1 knockout lines generated with the CRISPR-Cas9 system showed lower ROS accumulation, higher ABA content, and a higher degree of stomatal closure than wild-type plants, leading to higher drought tolerance. Transcriptome sequencing data indicated that the significantly differentially expressed genes in the drought treatment group were mainly enriched in ABA signal transduction, antioxidant defense, and photosynthetic pathway. Taken together, the findings suggest that ZmASR1 negatively regulates drought tolerance and represents a candidate gene for genetic manipulation of drought resistance in maize.

Overexpressing plant ferredoxin-like protein enhances photosynthetic efficiency and carbohydrates accumulation in Phalaenopsis

Crassulacean acid metabolism (CAM) is one of three major models of carbon dioxide assimilation pathway with better water-use efficiency and slower photosynthetic efficiency in photosynthesis. Previous studies indicated that the gene of sweet pepper plant ferredoxin-like protein (PFLP) shows high homology to the ferredoxin-1(Fd-1) family that belongs to photosynthetic type Fd and involves in photosystem I. It is speculated that overexpressing pflp in the transgenic plant may enhance photosynthetic efficiency through the electron transport chain (ETC). To reveal the function of PFLP in photosynthetic efficiency, pflp transgenic Phalaenopsis, a CAM plant, was generated to analyze photosynthetic markers. Transgenic plants exhibited 1.2-folds of electron transport rate than that of wild type (WT), and higher CO2 assimilation rates up to 1.6 and 1.5-folds samples at 4 pm and 10 pm respectively. Enzyme activity of phosphoenolpyruvate carboxylase (PEPC) was increased to 5.9-folds in Phase III, and NAD+-linked malic enzyme (NAD+-ME) activity increased 1.4-folds in Phase IV in transgenic plants. The photosynthesis products were analyzed between transgenic plants and WT. Soluble sugars contents such as glucose, fructose, and sucrose were found to significantly increase to 1.2, 1.8, and 1.3-folds higher in transgenic plants. The starch grains were also accumulated up to 1.4-folds in transgenic plants than that of WT. These results indicated that overexpressing pflp in transgenic plants increases carbohydrates accumulation by enhancing electron transport flow during photosynthesis. This is the first evidence for the PFLP function in CAM plants. Taken altogether, we suggest that pflp is an applicable gene for agriculture application that enhances electron transport chain efficiency during photosynthesis.

Deciphering the roles of unknown/uncharacterized genes in plant development and stress responses

In recent years, numerous genes that encode proteins with specific domains that participate in different biological processes or have different molecular functions have been identified. A class of genes with typical domains whose function has rarely been identified and another type of genes with no typical domains have attracted increasing attentions. As many of these so-called as unknown/uncharacterized (U/U) genes are involved in important processes, such as plant growth and plant stress resistance, there is much interest in deciphering their molecular roles. Here, we summarize our current understanding of these genes, including their structures, classifications, and roles in plant growth and stress resistance, summarize progress in the methods used to decipher the roles of these genes, and provide new research perspectives. Unveiling the molecular functions of unknown/uncharacterized genes may suggest strategies to fine-tune important physiological processes in plants, which will enrich the functional network system of plants and provide more possibilities for adaptive improvement of plants.

Overexpression of SmMYC2 enhances salt resistance in Arabidopsis thaliana and Salvia miltiorrhiza hairy roots

Soil salinity significantly affects both Salvia miltiorrhiza growth and development as well as seed germination throughout field cultivation and production. The basic helix-loop-helix (bHLH) transcription factor (TF) MYC2 contributes significantly to plant stress resistance as a key regulator of the jasmonic acid signaling pathway. In transgenic S. miltiorrhiza hairy roots, SmMYC2 has been shown to promote the accumulation of tanshinone and salvianolic acid, but its role in S. miltiorrhiza of resistance to abiotic stress is unclear. Herein, we found methyl jasmonate (MeJA), NaCl, and PEG treatment all significantly increased SmMYC2 expression. In response to salt stress, SmMYC2 overexpression in yeast increased its rate of growth. Additionally, overexpression of SmMYC2 transgenic Arabidopsis thaliana and S. miltiorrhiza hairy root showed that it might improve salt resistance in transgenic plant. In particular, compared to WT, overexpression of SmMYC2 transgenic Arabidopsis had higher levels of three antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), proline (Pro) content, and ABA-dependent and ABA-independent genes expression. They also had lower levels of malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation. What's more, overexpression of SmMYC2 increases the expression of flavonoid synthesis genes and the accumulation of related components in Arabidopsis. These findings imply that SmMYC2 functions as a positive regulator that regulates plant tolerance to salt through ABA-dependent and independent signaling pathways.

The red seaweed Kappaphycus alvarezii antiporter gene (KaNa+/H+) confers abiotic stress tolerance in transgenic tobacco

BACKGROUND

Plant establishment, growth, development and productivity are adversely affected by abiotic stresses that are dominant characteristics of environmentally challenged/degraded habitats created in the Anthropocene. Crop breeding for climate resilience properties is need of the hour to sustain the crop productivity. We report on the characterization of Kappaphycus alvarezii (a red seaweed) Na+/H+ antiporter gene (KaNa+/H+) for enhanced salt and osmotic stress tolerance.

METHODS

The KaNa+/H+ antiporter gene was cloned and over-expressed in tobacco under the control of CaMV35S promoter. Transgenic analysis was carried out to assess the stress tolerance ability of tobacco over-expressing KaNa+/H+ antiporter gene.

RESULTS

Over-expression of KaNa+/H+ gene improved the seed germination and seed vigor index under stress. Transgenic plants grew better and exhibited delayed leaf senescence. Improved K+/Na+, carotenoid/total chlorophyll and relative water content; lower accumulation of reactive oxygen species (ROS), MDA and Na+; lower electrolyte leakage; better membrane stability index and accumulation of K+, photosynthetic pigment, starch, sugar, free amino acid, proline and polyphenol contents indicated better physiological health of the transgenic tobacco under stress. Transgenic tobacco exhibited higher photosynthesis, photosystem II efficiency, electron transfer rate, photochemical quenching and activity of water splitting complex. Compared with control tobacco, transgenic tobacco exhibited higher expression of stress-defence genes under stress and better recovery after long-term osmotic stress.

CONCLUSIONS

Lower Na+ cytotoxicity, lower accumulation of ROS and maintenance of the membrane integrity helped transgenic tobacco to maintain the physiological functioning under stress. Present results established K. alvarezii as a potential gene resource and the KaNa+/H+ antiporter gene as a potential candidate gene in molecular breeding of crops for development of the degraded land.