The Center of Excellence for Molecular Plants of the Chinese Academy of Sciences completed the first spatial culture experiment of the whole life cycle of rice from seed to seed

On December 4, Beijing time, the Shenzhou 14 manned spacecraft return module successfully landed
at the Dongfeng landing site.
On the same day, rice and Arabidopsis seeds, which had undergone a full life cycle of 120 days, were delivered to the space application system
along with samples of other manned space science experiments.

 

Rice is humanity's main food crop, feeding nearly half of the world's population, and is a major candidate for future manned deep space exploration life support systems
.
The use of space microgravity for rice breeding is also one of the important directions of
space botany research.
Seeds are not only food for human beings, but also the carrier for reproducing the next generation of plants, and if human beings want to survive in space for a long time, they must ensure that plants can complete the generation of rotation in space and successfully reproduce seeds
.
However, previously, only the cultivation of Arabidopsis thaliana, rape, peas and wheat from seed to seed had been completed in space, while rice, the main food crop, had not been able to complete the full life cycle of rice in space
.

 

In the life science project of China's space station, the research team of Zheng Huiqiong of the Center for Excellence in Molecular Plant Science of the Chinese Academy of Sciences undertook the "molecular mechanism of flowering regulation of higher plants under microgravity conditions", and carried out the whole life cycle cultivation experiment
of rice from seed to seed for the first time in the world.
At the same time, flowering is the prerequisite for seeding, and the research team also systematically studied the effect of
spatial microgravity on plant flowering using the model plant Arabidopsis.

 

From the start of the experiment by injecting nutrient solution on July 29, 2022 to the end of the experiment on November 25, 2022, this project carried out a total of 120 days of experiments in orbit, and completed the cultivation experiment
of Arabidopsis thaliana and rice seed germination, seedling growth, flowering and seeding.
During this period, astronauts conducted three sample collections in orbit, including rice samples in the pregnant ear stage on September 21; Arabidopsis thaliana flowering samples were collected on 12 October and samples at the ripening stage of rice and Arabidopsis thaliana seeds on 25 November
.
After collection, samples at the flowering or pregnant stage were stored in a -80°C cryogenic storage cabinet, and seed ripening samples were stored in a 4°C cryogenic storage cabinet
.
On December 4, the sample returned to the ground
with Shenzhou XIV.
After handing over the samples in Beijing as planned, they were transferred to the Shanghai laboratory for further testing and analysis
.

 

The main experimental contents completed by this space project include: (1) the cultivation experiment of rice in orbit from seed germination, seedling growth, ear pumping and seed setting to the whole life cycle was completed and analyzed by acquiring images; (2) After the completion of cutting, the spatial regeneration rice was successfully cultivated and produced mature seeds (two stubbles); (3) The image observation and analysis of the spatial microgravity response of Arabidopsis thaliana seed germination, seedling growth and flowering key genes regulated by different three biological clocks were completed in orbit, and samples were collected in orbit
.

 

Through the analysis of spatially acquired images and comparison with ground controls, it is found that spatial microgravity has the effects
of various agronomic traits of rice, including plant height, tillering number, growth rate, water regulation, light response, flowering time, seed development process and setting rate.
Preliminary findings of the experiment:

 

(1) The plant type of rice becomes looser in space, mainly because the angle between stem and leaf becomes larger; Dwarf rice became shorter, and the height of tall stalk rice was not significantly affected
.
In addition, the spiraling movement of rice leaf growth controlled by the biological clock is more prominent
in space.

 

(2) The spatial flowering time of rice is slightly earlier than that of the ground, but the filling time is extended by more than 10 days, and most of the shells cannot be closed (Figures 1 and 3).

Flowering time and shell closure are important agronomic traits of rice, both of which play an important role in ensuring adequate reproductive growth of plants and obtaining high-yield and high-quality seeds, which are regulated by gene expression and will be further analyzed
using the returned samples.

 

(3) Conduct regenerative rice experiments in space and obtain seeds of regenerated rice
.
Two rice ears can be regenerated 20 days after cutting (Figures 2 and 3), indicating that rice regeneration in a closed environment with limited space is feasible, and providing new ideas and experimental evidence
for the efficient production of space crops.
This technology can greatly increase the yield of rice in the volume, and it is also the first regenerative rice technology
in the world to be tried in space.

 

(4) For the first time, the key genes of the space circadian clock regulating photoperiod flowering were studied
.
Using gene mutation and transgenic methods, three Arabidopsis thaliana with different flowering times were constructed, namely: early flowering, delayed flowering and normal flowering (wild type), through the observation and analysis of the growth and development of Arabidopsis thaliana in space, it was found that the response of key genes of flowering to microgravity was significantly different from that on the ground, and the flowering time of Arabidopsis thaliana with early flowering on the ground was also greatly extended
under microgravity conditions 。 In addition, the hypocotyl of Arabidopsis thaliana was over-elongated after the mutation of the biological clock gene, indicating that the expression of the biological clock gene was very important for maintaining the normal morphology of Arabidopsis thaliana growth in space and adapting to the space environment, which provided a new direction
for the future use of modified flowering genes to promote the adaptation of plants to the space microgravity environment.
The follow-up research team will further use the returned materials to further analyze
the molecular basis of Arabidopsis thaliana adaptation to the space environment.