Flowering mechanism in Brassica rapa leafy vegetables illuminated

November 10, 2019

Post graduate students in Kobe University's Graduate School of Agricultural Science have revealed the role of genes in controlling flowering time in the Brassica rapa family. Satoko Takada and Ayasha Akter demonstrated that a higher level of FLC gene expression is essential for inhibiting flowering in the absence of a cold period. They also discovered that the rate of repression of FLC expression during a cold exposure affects the flowering time. It is hoped that this understanding can contribute to the efficiency of B. rapa vegetable cultivation in the face of climate change.

The cross-institutional research group also consisted of Associate Professor Ryo Fujimoto (Graduate School of Agricultural Science), Professor Keiichi Okazaki and Researcher Daniel Shea (both of Niigata University Graduate School of Science and Technology), NARO Japan, and members from CSIRO Australia.

These results were first published in the Scientific Reports journal on September 25, 2019.

Introduction

The B. rapa family is made up of leafy and root vegetables. Varieties of B. rapa include Chinese cabbage, pak choi, turnip and komatsuna. These plants require vernalization in order to flower. Vernalization is a period of prolonged cold exposure which triggers flowering. This has traditionally enabled plants to avoid flowering during winter and instead bloom during more favorable spring weather.

Regulating flowering time is important for plant breeding. Alterations to flowering time can increase the cultivation period and improve tolerance against changes in climate conditions. It can also reduce bolting- which is when plants flower too early. Understanding the vernalization mechanism in B. rapa vegetables is important for efficient cultivation.

Extensive studies into the vernalization mechanism in Arabidopsis thaliana (At) have found that there are two genes that play an important role in regulating flowering time- FRIGIDA (FRI) and FLOWERING LOCUS C (FLC). The FRI gene in A. thaliana (AtFRI) regulates the AtFLC gene responsible for flowering. Before the plant is exposed to cold temperatures, AtFRI causes the AtFLC gene to be expressed, preventing flowering. Subsequent vernalization causes the AtFLC gene to be inhibited, thus allowing A. thaliana to flower (see Figure 1).

The current study sought to illuminate how the FRI and FLC genes are involved in this process in B. rapa and to understand their role in early flowering and late flowering lines.

Methodology

The research group discovered two FRI genes (BrFRIa, BrFRIb) and four FLC genes (BrFLC1, BrFLC2, BrFLC3, BrFLC5) in B. rapa. Next, studies were conducted to determine the function of these genes using A. thaliana as a model.

The A. thaliana used was an early flowering model with no AtFRI function and therefore no AtFLC expression. When the B. rapa gene BrFRIb was transformed into this early flowering A. thaliana, this triggered the expression of AtFLC, thus making the plant late flowering. This shows that BrFRIb has an FLC triggering function (Figure 2). Subsequent experiments on this early flowering A. thaliana revealed that the B. rapa genes BrFLC1, BrFLC2 and BrFLC3 all caused the plant to become late flowering. This showed that all three of these BrFLC genes are floral repressors.

Next, the researchers investigated how long nine lines of B. rapa took to flower after being exposed to cold (4?) for 4 weeks. After the cold treatment, the plants were transferred to soil and grown in normal conditions (at 22?). The number of days required to flower was measured. As shown in Figure 3, lines such as Homei were early flowering while Harunosaiten and BRA2209 were late flowering.

In order to determine the impact of BrFLC genes on the vernalization requirements of B. rapa, the expression levels of BrFLC genes in these nine lines were measured. It was found that during cold exposure, early flowering varieties contained low levels of BrFLC expression and late flowering varieties contained high levels of BrFLC expression. This shows that BrFLC expression levels are associated with flowering time.

Conclusion

Resistance to bolting in B. rapa is an important trait for the successful cultivation of these vegetables. The results revealed that in order to prevent cabbage, komatsuna and turnips from flowering while it is still cold, a high quantitative expression of BrFLC genes is needed prior to cold exposure.
-end-


Kobe University

Related Vegetables Articles from Brightsurf:

One third of UK fruit and vegetables are imported from climate-vulnerable countries
One third of UK fruit and vegetables are imported from climate-vulnerable countries - and this is on the rise.

Eating your vegetables is easier said than done
The landmark EAT-Lancet report on food in the Anthropocene sets ambitious targets.

Research shows that the combined production of fish and vegetables can be profitable
When it comes to future food production, the combined farming of fish and vegetables through aquaponics is currently a hotly debated topic.

Sensitivity to bitter tastes may be why some people eat fewer vegetables
A gene that makes some compounds taste bitter may make it harder for some people to add heart-healthy vegetables to their diet.

Flowering mechanism in Brassica rapa leafy vegetables illuminated
Post graduate students in Kobe University's Graduate School of Agricultural Science have revealed the role of genes in controlling flowering time in the Brassica rapa family.

Offering children a variety of vegetables increases acceptance
Although food preferences are largely learned, dislike is the main reason parents stop offering or serving their children foods like vegetables.

Cooking vegetables: healthier with extra virgin olive oil
Cooking vegetables in the sofrito (sauté) with extra virgin olive oil favours the absorption and release of bioactive compounds of its traditional ingredients (garlic, onion and tomato), according to the study published in the journal Molecules about the role of gastronomy in the health-improving effects of the Mediterranean Diet.

Millions of cardiovascular deaths attributed to not eating enough fruits and vegetables
Preliminary findings from a new study reveal that inadequate fruit and vegetable consumption may account for millions of deaths from heart disease and strokes each year.

Tuck into colourful fruits and vegetables and see the light
A $5.7 billion global medical bill to restore sight for the estimated 45 million people with cataracts could be slashed in half by a diet rich in colourful fruits and vegetables, according to an international study.

Canadians' consumption of fruit and vegetables drops 13 per cent in 11 years
Two surveys taken 11 years apart show a 13-per-cent decrease in the amount of fruit and vegetables being consumed by Canadians, new University of British Columbia research has found.

Read More: Vegetables News and Vegetables Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.