Recent advances in utilizing transcription factors to improve plant abiotic stress tolerance by transgenic technology

Agricultural production and quality are adversely affected by various abiotic stresses worldwide and this will be exacerbated by the deterioration of global climate. To feed a growing world population, it is very urgent to breed stress-tolerant crops with higher yields and improved qualities against multiple environmental stresses. Since conventional breeding approaches had marginal success due to the complexity of stress tolerance traits, the transgenic approach is now being popularly used to breed stress-tolerant crops. So identifying and characterizing the the critical genes involved in plant stress responses is an essential prerequisite for engineering stress-tolerant crops. Far beyond the manipulation of single functional gene, engineering certain regulatory genes has emerged as an effective strategy now for controlling the expression of many stress-responsive genes. Transcription factors (TFs) are good candidates for genetic engineering to breed stress-tolerant crop because of their role as master regulators of many stress-responsive genes. Many TFs belonging to families AP2/EREBP, MYB, WRKY, NAC, bZIP have been found to be involved in various abiotic stresses and some TF genes have also been engineered to improve stress tolerance in model and crop plants. In this review, we take five large families of TFs as examples and review the recent progress of TFs involved in plant abiotic stress responses and their potential utilization to improve multiple stress tolerance of crops in the field conditions

Proline accumulation and metabolism-related genes expression profiles in Kosteletzkya virginica seedlings under salt stress

Proline accumulation is a common response to salt stress in many plants. Salt stress also increased proline concentration in roots, stems and leaves of Kosteletzkya virginica seedling treated with 300mM NaCl for 24h and reached 3.75, 4.76 and 6.83 fold higher than controls. Further study on proline content in leaves under salt stress showed that proline content increased with increasing NaCl concentrations or time. The proline level peaked at 300 mM NaCl for 24h and reached more than 6-fold higher than control, but at 400mM NaCl for 24h proline content fell back slightly along with wilting symptom. To explore the cause behind proline accumulation, we first cloned full length genes related to proline metabolism including KvP5CS1, KvOAT, KvPDH, KvProT from Kosteletzkya virginica and investigated their expression profiles. The results revealed that the expressions of KvP5CS1 and KvProT were sharply up-regulated by salt stress and the expression of KvOAT showed a slight increase with increasing salt concentrations or time, while the expression of KvPDH was not changed much and slightly decreased before 12h and then returned to the original level. As the key enzyme genes for proline biosynthesis, the up-regulated expression of KvP5CS1 played a more important role than KvOAT for proline accumulation in leaves under salt stress. The low expression of KvPDH for proline catabolism also made a contribution to proline accumulation before 12h

NAC transcription factors in plant multiple abiotic stress responses：progress and prospects

Abiotic stresses adversely affect plant growth and agricultural productivity. According to the current climate prediction models, crop plants will face a greater number of environmental stresses, which are likely to occur simultaneously in the future. So it is very urgent to breed broad-spectrum tolerant crops in order to meet an increasing demand for food productivity due to global population increase. As one of the largest families of transcription factors in plants, NAC transcription factors play vital roles in regulating plant growth and development processes including abiotic stress responses. Lots of studies indicated that many stress-responsive NAC transcription factors had been used to improve stress tolerance in crop plants by genetic engineering. In this review, the recent progress in NAC transcription factors was summarized, and the potential utilization of NAC transcription factors in breeding abiotic stress tolerant transgenic crops was also be discussed. In view of the complexity of field conditions and the specificity in multiple stress responses, we suggest that the NAC TFs commonly induced by multiple stresses should be promising candidates to produce plants with enhanced multiple stress tolerance. Furthermore, the field evaluation of transgenic crops harboring NAC genes, as well as the suitable promoters for minimizing the negative effects caused by over-expressing some NAC genes, should be considered

Soybean C2H2-type zinc finger protein GmZFP3 with conserved QALGGH motif negatively regulates drought responses in transgenic Arabidopsis

Plant response to environmental stresses is regulated by a complicated network of regulatory and functional genes. In this study, we isolated the putative stress-associated gene GmZFP3 (a C2H2-type Zinc finger protein gene) based on the previous finding that it was one of two genes located in the QTL region between the Satt590 and Satt567 markers related to soybean tolerance to drought. Temporal and spatial expression analysis using quantitative real-time PCR indicated that GmZFP3 was primarily expressed in roots, stems and leaf organs and was expressed at low levels in flowers and soybean pods. Moreover, GmZFP3 expression increased in response to polyethylene glycol(PEG) and Abscisic acid(ABA) treatments. In addition, subcellular localization analysis indicated that GmZFP3 was ubiquitously distributed in plant cells. Transgenic experiments indicated that GmZFP3 played a negative role in plant tolerance to drought. Analysis of ABA-related marker gene expression in Arabidopsis suggested that GmZFP3 might be involved in the ABA-dependent pathway during the drought stress response. Taken together, these results suggest that soybean GmZFP3 negatively regulates the drought response

A novel soybean intrinsic protein gene, GmTIP2;3, involved in responding to osmotic stress

Water is essential for plant growth and development. Water deficiency leads to loss of yield and decreased crop quality. To understand water transport mechanisms in plants, we cloned and characterized a novel tonoplast intrinsic protein (TIP) gene from soybean with the highest similarity to TIP2-type from other plants, thus designated GmTIP2;3. The protein sequence contains two conserved NPA motifs and six transmembrane domains. The expression analysis indicated that this gene was constitutively expressed in all detected tissues, with higher levels in the root, stem and pod, and the accumulation of GmTIP2;3 transcript showed a significant response to osmotic stresses, including 20% PEG6000 (polyethylene glycol) and 100 µM ABA (abscisic acid) treatments. The promoter-GUS (glucuronidase) activity analysis suggested that GmTIP2;3 was also expressed in the root, stem and leaf and preferentially expressed in the stele of root and stem, and the core promoter region was 1000 bp in length, located upstream of the ATG start codon. The GUS tissue and induced expression observations were consistent with the findings in soybean. In addition, subcellular localization showed that GmTIP2;3 was a plasma membrane-localized protein. Yeast heterologous expression revealed that GmTIP2;3 could improve tolerance to osmotic stress in yeast cells. Integrating these results, GmTIP2;3 might play an important role in response to osmotic stress in plants