■ Introduction to Research〓 Research Area : Plant Genome Dynamics Analysis

Study on genetic and genomic analyses for plant
breeding
We are engaged in genetic and breeding research by using next-generation sequencing technology (NGS) for various crop species. Our research has been mainly conducted on the hexaploid

crop species called sweetpotato (Ipomoea batatas (L.) Lam.). Sweetpotato is one of the mostimportant crop species in the world, and the annual production in the world exceeds 100 million

tons (FAO). There is a need to develop high value-added varieties to which excellent traits suchas pest resistance, yield and taste have been imparted. However, sweetpotato is geneticallycomplicated, and its genetic analysis has been considered extremely difficult. In such a situa-tion, our groups succeeded in genome-wide genetic analysis by using NGS in sweetpotato. We
identified genetic regions related to agricultural traits such as disease and pest resistance byperforming QTL analysis and GWAS (Genome-wide association study). Using these research
results, we developed selective DNA markers useful for breeding.

〓 Assoc. Prof.
MONDEN Yuki〓 Research Area : Plant Pathology

Unrabeling plant disease susceptibility to fungal
pathogens

Multi-layered defense barriers ensure that a plant is the host to only a few adapted pathogens.
Thus, the host range of a particular plant pathogen relies on its ability to fully suppress plant
defense responses such as the pattern-triggered immunity (PTI). One of the common pathogen
strategies to overcome PTI is the production of a plant defense suppressor. In the case of Mycosphaerella pinodes , a causal agent of Mycosphaerella blight on pea, this fungus can avoid hostdefense responses by secreting at least two suppressors named supprescins A and B (Fig. 1),
which manipulate the physiology of the host cells, including JA biosynthesis through targetingthe host’s ATPase. In parallel, a constituent(s) similar to the fungal supprescins has been discovered in healthy leaves of pea. Such a constituent was also found in the healthy leaves of barleyand Arabidopsis plants, and collectively referred to as an endogenous suppressor (ES). Actually,
the purified ES can suppress or delay PTI, enabling the non-adapted pathogen to cause disease
symptom on corresponding plants. Interestingly, the action of the pea ES is quite similar to thatof the supprescins A and B secreted by M. pinodes . Consistently, the ES can severely inhibit
host’s ATPase, temporarily reducing the ability of the host cell to defend itself. The putative roleof the ES is assumed to be involved in the trade-offs between plant growth and defense by preventing excessive defense responses against pathogen attack. Alternatively, it is likely used bya pathogen to promote disease susceptibility. We are now focusing on the host cell physiology
altered by a pathogen- and/or plant-derived suppressors in relation to the convergent evolution
between pathogen and host.

〓 Prof.
TOYODA Kazuhiro

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Chemical structures ofFig. 1.
Supprescins A and B from Mycoso phaerella pinodes . (a) Chemical structures of Supprescin A (upper ) and B(lower ). The common moiety consistingof O-glycosyl portion attached to theserine (GalNAc-Ser-Ser-Gly) is proposed to be essential for suppressor activity. (b) A predicted structure (left ) of the Supprescin B, a major
suppressor of M. pinodes and its distribution of charge around this molecule (right ).