Aims to understand the Way of Communication at the Plant Surface

Question 1 Would you mind to explain us your research aim?

In my research, I’m using interspecies pollinations between rice and wild rice to look at interactions of pollen with the stigma and the growth of pollen tubes to the ovaries.

In the case of pollen and stigma interactions, the question is “how can stigma recognise that this is correct pollen? – is this pollen? And is this the correct pollen?” The pollen grows a pollen tube into the stigma and how does the pollen tube know where to go? It is a matter of communication. The stigma recognises the pollen and the pollen recognises the stigma. I want to find out the mechanism of recognition, and guidance also – how the pollen tube finds the correct route in the pistil. In rice, we don’t know so much about how that happens.  

I’ve looked at pollen tube growth in interspecies pollinations between wild and cultivated rice and identified some barriers to the pollen tube growth-i.e. locations where the pollen tubes fail to extend when the pollen and pistil are not from the same species. If there is such a barrier it means there is failure in communication and recognition between the pollen and the pistil. Perhaps at that location there is a mechanism to guide or recognize the pollen tube, which fails when the pollen and pistil are of different species.

In fact, I found that Oryza sativa pollen could not get past the stigma in Oryza punctata pistils, and in Oryza officinalis pistils, the O.sativa pollen tubes grew through the stigma, but subsequently stopped growing in the style, sometimes swelling or branching, too. Now I have prepared RNA from Oryza sativa and Oryza officinalis in stigma, styles and pistils, and if I can compare gene expressions between two different stigmas, then I can find some candidate genes which may be involved in controlling pollen-pistil interactions in rice.

One class of genes which might be candidates are small, cysteine-rich proteins. It’s been noticed previously that a lot of this type of genes are expressed in reproductive tissues in plants. Some of the proteins encoded by those genes have been shown to be important for pollen-pistil interactions in some species. Notably, many of the proteins are similar in structure to defence related proteins-components of the plant immune system.

Actually, immune systems and reproductive systems have a similar property – they have to recognise and reject something – whether that is inappropriate pollen, from the wrong species, or a pathogen attempting to invade. So maybe it is not so surprising that recognition systems in both cases may be similar, perhaps having common evolutionary origins, even maybe sharing components.

For these reasons, I’m performing a genome-wide survey of small secreted cysteine-rich proteins from available Oryza genomes. The evolution of these small proteins looks interesting. It seems that plant genomes contain large numbers of potentially redundant proteins which might function together.
So genomic plasticity might be a way in which new specificity in defence or reproduction may arise.

I took the genome sequences of three types of cultivated rice, Oryza sativa japonica, Oryza sativa indica andOryza glaberrima (African rice) along with three different accessions of Oryza rufipogon (Asian wild rice, the species from which Oryza sativa was domesticated) and searched for small cysteine rich protein genes. Then I compared the genes across the six genomes. While all the genomes contained similar types of cysteine rich protein gene families in similar positions on the chromosomes, often the gene sequences were disrupted, or missing altogether in one or more species. Gene duplication was also common. By contrast, variation in the actual coding sequences was small. So it seems the difference in the small cysteine rich proteins across the species is mainly due to gain or loss of functional genes, rather than variation in the protein sequences themselves. 

In the recognition between pistils and pollen, we don’t necessarily think about one single protein or only two proteins. Probably we think of many different molecules on one side and many molecules on another side. Together this kind of molecular dialogue makes for recognition or non- recognition. Probably several of these gene products are acting together contributing to the specificity of the pistil pollen interaction. In the case of interspecies pollination, failure of pollen tube growth may be due to the absence of particular cysteine rich proteins in one or other of the species. If I can identify the small cysteine-rich protein genes which are expressed species-specifically in the pistil, then maybe I can go some way to identify components in the recognition and guidance between pistil and pollen tubes in rice.

Question 2 How did you know NIG?

When I first came to Japan, I was working at IBRC in Iwate Prefecture. So I didn’t really know about this part of Japan. I think the first I knew about NIG was when we got some seeds for wild rice species, which came from the NBRP collection. 

Question 3　What is a merit of working/ studying at NIG?

There are many good reasons to come to NIG. There are a lot of benefits. As it is a national institute, the quality is very high all around, in a lot of different areas, so you can learn a lot from seminars, talks and other meetings. There is always interesting science in varied areas and people are very experienced to discuss or to learn from.
Besides those people who are working here, many great international scientists – even Nobel Prize winners visit and give us seminars. I really enjoy hearing their talk and to me it’s rewarding.
From seminars I sometimes get hints, sometimes know contexts about different type of science and sometimes inspiration.

The other thing is as international researchers who are not fluent in Japanese, it is good and helpful because most of the science is done in English, and there are also quite a few other international students and researchers around. It is good to talk to such people in the same situation. For me it meant it was easy to start my collaboration with other members in NIG. 

Question 4　What is your impression of Mishima city?

I like Mishima. Mishima is a nice and quiet town. There are shops and nice things to eat here. Good place for family. I grew up in the countryside, so for me it’s nice to be close to fields, trees and mountains – and of course having a daily view of Mt. Fuji is very special. I lived in Mishima for a few years, still to see Mt. Fuji is very impressive.
The location is also great for access to Tokyo and other cities. Being in the central of Japan is a very convenient for lots of reasons.
The weather is a big bonus although being British, Mishima is little too hot. In England, we don’t have such high temperature or high humidity. 

Question 5 How do you spend your day off/ holiday?

I play the oboe – I’ve performed in two concerts with Mishima Philharmonic Orchestra. Orchestra is all about combination of different sounds. To play music together is most exciting part of playing. Especially it’s rewarding because even though I can’t communicate well with all members in Japanese, I can still play together and music still works.
I also like road cycling so I like to get into the Izu peninsula and ride some mountain roads. Last time I cycled to Shuzenji then Daruma-Yama and Heda-toge. The route by the coast is spectacular.

Besides that, spending time with my family, gardening, cooking vegetables freshly taken from our garden, eating out, BBQ, and playing soccer with the boys… I like lots of things and enjoy doing them but not much time! But I much prefer to be busy than not to be busy, so when an opportunity comes up, I just do it.  

Question 6 What would you like to achieve in the future?

I’m lucky to be here. I’m hoping for some nice success which can contribute to the society in my work as I would like to settle down permanently in Japan with my family. 

transcription & translation : Chikako Miura　(General Affairs/Education Team)

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