Differentially Expressed Genes Associated with Improved Drought Tolerance in Creeping Bentgrass Overexpressing a Gene for Cytokinin Biosynthesis

Abstract

Transformation with an isopentenyl transferase (ipt) gene controlling cytokinin (CK) synthesis has been shown to enhance plant drought tolerance. The objective of this study was to identify differentially-expressed genes (DEGs) in creeping bentgrass (Agrostis stolonifera) overexpressing ipt compared to non-transgenic plants. The ipt transgene was controlled by a senescence-activated promoter (SAG12). Both a null transformed line (NT) and SAG12-ipt plants were exposed to drought stress in an environmentally-controlled growth chamber until the soil water content declined to approximately 5% and leaf relative water content declined to 47%, which were both significantly below the well-watered controls. RNA was extracted from leaf samples of both well-watered and drought-stressed plants. Eight sets of subtractive hybridizations were performed for detection of up-regulated and down-regulated genes due to the presence of the transgene and due to drought stress in both NT and transgenic plants. Sequencing analysis revealed the identity of 252 DEGs due to either the transgene and drought stress. Sequencing analysis of 170 DEGs identified genes encoding for proteins that were related to energy production, metabolism, stress defense, signaling, protein synthesis and transport, and membrane transport could play major roles in the improved drought tolerance by overexpressing ipt in creeping bentgrass.

Transcriptomic signature of drought response in pearl millet (Pennisetum glaucum (L.) and development of web-genomic resources

“…In drought response, there is change in energy balance and metabolic pattern. Genes controlling these activities were found differentially expressed in our dataset, for example, LEA (Late Embryogenesis Abundant) gene reported to be associated with salt stress 67 , ATP (Adenosine Triphosphate) citrate synthase reported to control energy balance in drought 68 , aspartate kinase-homoserine dehydrogenase reported to control tricarboxylic acid (TCA) cycle 69 , glycolysis and Krebs cycle controlled by NADP dependent malic enzyme gene 70 . High affinity of nitrate transport uptake has been reported in drought treated roots and the same was observed in differential expression of nitrate transporter gene 59 .…”

Role and Regulation of Cytokinins in Plant Response to Drought Stress

“…Drought-responsive genes play important roles in plant adaptation under drought stress conditions. However, the molecular mechanisms related to CKs behind this process remain uncertain [151]. Previous genome-wide analyses have shown that altering the endogenous CK levels by modulating the expression of either IPT or CKX genes could affect the expression of several sets of genes involved in different processes that could play major roles in improved drought tolerance.…”

“…Previous genome-wide analyses have shown that altering the endogenous CK levels by modulating the expression of either IPT or CKX genes could affect the expression of several sets of genes involved in different processes that could play major roles in improved drought tolerance. Examples of these various processes include energy production, metabolic activities, stress defense, signaling, protein synthesis and transport, and membrane transport [74,75,126,151]. Molecular analyses in creeping bentgrass overexpressing CK biosynthesis-related gene IPT from A. tumefaciens under the control of the SAG12 promoter revealed the expression of genes encoding proteins with different functions such as CAT (ROS detoxification), RuBisCo large subunit (energy production), Leu-rich repeat (LRR) receptor-like kinase (transmembrane receptor proteins), oxygen-evolving enhancer protein 3-1 and chloroplast precursor (OEE3) (metabolism), and universal stress protein 5327 (stress defense) [151].…”

“…Examples of these various processes include energy production, metabolic activities, stress defense, signaling, protein synthesis and transport, and membrane transport [74,75,126,151]. Molecular analyses in creeping bentgrass overexpressing CK biosynthesis-related gene IPT from A. tumefaciens under the control of the SAG12 promoter revealed the expression of genes encoding proteins with different functions such as CAT (ROS detoxification), RuBisCo large subunit (energy production), Leu-rich repeat (LRR) receptor-like kinase (transmembrane receptor proteins), oxygen-evolving enhancer protein 3-1 and chloroplast precursor (OEE3) (metabolism), and universal stress protein 5327 (stress defense) [151]. In addition, transgenic creeping bentgrass harboring P SAG12 ::IPT showed induced the expression of TF-encoding genes such as bHLH148, MYB4/4-like, and WRKY28/53/71 under drought, which can lead to the initiation of defensive responses, including protein modification and degradation, RNA degradation, or JA-and ABA-regulated responses [126].…”

The Mode of Cytokinin Functions Assisting Plant Adaptations to Osmotic Stresses

“…Substantially higher transcript levels were observed for genes encoding proteins like Mg-protoporphyrin IX, chloroplast localized ToxA binding protein (Pr ToxA), CAT, aquaporin Pip1-2, Leu-rich repeat (LRR) receptor kinases, universal stress protein (USP), and isoflavone reductase-like protein 5. Conversely, transgenic plants showed reduced transcript levels of genes encoding malate dehydrogenase, glycogen synthase kinase (GSK), DELLA proteins, and ATP binding cassette (ABC) transporters [113]. To identify transcription factors (TFs) and their downstream genes associated with high CK mediated drought acclimation, transcriptomic profiling of IPT-transgenic creeping bentgrass was performed under drought stress.…”