Assessing Radish Health during Space Cultivation by Gene Transcription

Area of Science:

• Plant biology
• Space biology
• Molecular biology

Background:

• Radish plants (Raphanus sativus) were cultivated on the International Space Station (ISS) for two 27-day growth cycles.
• Gene expression analysis was performed on leaf and bulb samples, comparing space-flown specimens with ground controls (GC).
• Ground controls were maintained at Kennedy Space Center (KSC) under ISS conditions, including elevated CO2, and a separate lab control used ambient CO2.

Purpose of the Study:

• To investigate and compare gene transcription profiles of radish plants grown in space versus on Earth.
• To evaluate the impact of spaceflight on plant development and gene expression using multiple analytical methods.
• To compare the efficacy of quantitative polymerase chain reaction (qPCR) and RNA sequencing (RNA-seq) for analyzing space-flown plant samples.

Main Methods:

• Leaf punch (LP) and bulb tissue samples were collected at various time points and harvest.
• Gene expression was quantified using qPCR for specific genes: peroxidase (RPP), glucosinolate biosynthesis (GIS), protein binding (CBP), myrosinase (RMA), napin (RSN), and ubiquitin (UBQ).
• Solid Phase Gene Extraction (SPGE) probes and RNA-sequencing were employed for comprehensive gene expression profiling.

Main Results:

• Leaf punch samples from ISS-grown plants exhibited decreasing transcription values, suggesting potential stress, unlike stable GC samples.
• Solid Phase Gene Extraction (SPGE) results showed similarities between space-flown and ground control samples.
• RNA-sequencing revealed distinct transcription profiles compared to qPCR and LP data, potentially due to localized sampling or different temporal resolutions.

Conclusions:

• Space-grown radish plants may experience transcriptional stress compared to ground controls, as indicated by leaf punch sample analysis.
• While SPGE provided consistent results, RNA-seq offered a broader view of transcription, highlighting potential sampling method impacts.
• This study provides a foundational comparison of gene expression analysis techniques for space-flown plants, revealing subtle developmental changes.