Enhanced Photosynthesis and Water-Use Efficiency in Transgenic Sugarcane Expressing Arabidopsis DREB1A Under Drought Stress

Summary

This study evaluates Arabidopsis DREB1A-mediated drought tolerance in transgenic sugarcane. Under stress, enhanced photosynthesis, water-use efficiency, and biomass accumulation were observed. DR-21 exhibited the highest DREB1A expression, improving drought resilience. The findings provide insights into molecular mechanisms and offer a potential strategy for developing climate-resilient sugarcane varieties in water-limited regions.

Abstract

Drought stress imposes a critical limitation on sugarcane productivity, thereby necessitating the development of stress-resilient cultivars for sustainable agriculture. The present study aimed to enhance drought tolerance in sugarcane by introducing the Arabidopsis DREB1A gene under the control of the stress-inducible rd29A promoter. Transgenic sugarcane lines were generated via particle bombardment-mediated transformation and subsequently evaluated through molecular, physiological, and agronomic assessments under controlled and drought-stressed conditions.

Molecular analysis confirmed stable transgene integration, with transgenic lines exhibiting up to a 10-fold increase in DREB1A expression relative to wild-type plants. Physiological assessments demonstrated that, under drought stress at 60% field capacity (FC), transgenic lines maintained photosynthetic rates (P_N) that were 224-270% higher, stomatal conductance (g_s) increased by 84-167%, and relative water content (RWC) was enhanced by 25-31% compared to non-transgenic controls. Moreover, the leaves of transgenic sugarcane displayed improved osmotic regulation and water-use efficiency. Agronomic evaluations further revealed significant improvements in plant growth and productivity. Under drought stress (60% FC), transgenic lines exhibited 76-109% greater cane height, with cane diameter 71-86% larger. Shoot biomass increased by 39-87%, and root biomass was enhanced by 65-103%.

Additionally, the Brix percentage, indicative of sucrose accumulation, increased by 36-55% in the transgenic plants at 60% FC. These findings establish a robust correlation between DREB1A expression, enhanced physiological resilience, and improved agronomic performance under drought conditions. The capacity of DREB1A-expressing transgenic sugarcane to sustain higher photosynthetic activity, superior water-use efficiency, and increased biomass accumulation underscores its potential as a genetic strategy for developing drought-resilient sugarcane varieties. This study offers novel insights into the molecular mechanisms underlying drought tolerance and provides a promising approach for ensuring sustainable sugarcane cultivation in water-scarce regions.

Introduction

Sugarcane (Saccharum officinarum L.) is Pakistan's second major cash crop, primarily cultivated for its high sucrose content. However, optimal production is rarely achieved due to periodic water shortages^1,2. It is a member of the Poaceae grass family and is grouped in the PACCAD clade of the subfamily Panicoideae³. Members of this clade are often referred to as warm-season grasses and exhibit a C₄ photosynthetic system⁴. The primary mode of CO₂ fixation in sugarcane is C₄ photosynthesis with minimum....

Protocol

Generation of rd29A: DREB1A expression vector (Figure 1)
The full-length DREB1A open reading frame (ORF, 651 bp) was amplified from Arabidopsis thaliana L. cDNA using gene-specific primers incorporating BamHI and EcoRI restriction sites: forward 5^/-GGCGGATCCATGAACTCATTTTCTGCT-3^/ and reverse 5^/-GGCGAATTCTTAATAACTCCATAACGA-3^/. Similarly, the rd29A promoter (499 bp) was amplified from Arabidopsis genomic DNA using primers containing KpnI and BamHI sites: forw....

Results

Molecular characterization of sugarcane transgenic lines
The rd29A: DREB1A expression cassette was constructed and cloned in the plant-expressible binary vector pGA482 (Figure 1), which was then transformed into the sugarcane genome using the biolistic-mediated transformation technique and successfully developed transgenic sugarcane plantlets as described (Figure 2). The presence of transgenes in sugarcane lines was confirmed by amp.......

Discussion

Developing water stress tolerance in plants is crucial due to the ongoing expansion of drought-prone regions worldwide. As a potentially feasible biotechnological approach, we studied the role of DREB1A in water stress tolerance in transgenic sugarcane lines. Previous studies have reported the role of the DREB1A transcription factor in inducing the expression of multiple genes that confer tolerance to abiotic stress^28,38,

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cloning vector, pTZ57R/T	Fermentas, Vilnius, Lithuania
infrared gas-exchange analyzer	Bio-Rad, California, USA
Osmometer	Bio-Rad, California, USA
PCR machine	Bio-Rad, California, USA
PDS-1000/He Biolistic gun	ThermoFisher Sceintific Inc, USA
Real-time PCR	ThermoFisher Sceintific Inc, USA
RevertAid cDNA Synthesis Kit	CI-340, CID Bio-Science, Inc., USA
Scholander-type pressure chamber	Skye instruments, Llandrindod Wells, Birmingham, UK
TRIzol reagent	Wescor-5500, Logan, Utah, USA