Research Areas

Plant Molecular Physiology and Plant Development

This research direction includes two parts:
(1) Aiming at key scientific problems in the field of plant nutrition and metabolism, NKLPMG does further studies on the mechanism of terpene biosynthesis and plant-mediated insect RNA interference, plant nutrition and environmental adaptation, mechanism of photosynthesis, cell wall formation and biomass biosynthesis, metabolite synthesis and structural biology, etc.
(2) The lab uses Arabidopsis, rice, maize and cabbage as model plants to focus on the effects and functional mechanisms of plant developmental timing and life cycle strategy, light regulated development, senescence regulated by NO signal pathway, ethylene signal transduction, plant stem cells and regeneration.
These works are to understand molecular mechanisms underlying physiological and developmental processes in plant growth.

Primary Scientific Discoveries

Functionally characterized the QTL controlling Cd accumulation in rice leaves, and proposed and systematically elaborated the concept of “remediation-crops”
A worldwide concern nowadays is how to balance between food production and environmental remediation when more and more soil is polluted by toxic heavy metals. In our country, food security is an overwhelming concern, thus food safety usually has to be sacrificed and the moderately polluted land has to be used to produce food instead of being remediated. A potential solution to this problem might lie in the molecular breeding of "remediation-crops", which target metal accumulation to straws hence playing a dual role in phytoremediation and meanwhile producing safe grains. By ionomically profiling metal accumulation in a core collection of rice accessions in China and further map-based cloning, the research group led by Dr. Jiming Gong identified a rice quantitative trait locus CAL1 (Cadmium Accumulation in Leaf 1), which encodes a defensin-like protein. CAL1 is expressed preferentially in root exodermis and xylem parenchyma cells. They provided evidences to demonstrate that CAL1 acts by chelating Cd in the cytosol and hence facilitating Cd secretion to extracellular spaces, lowering cytosolic Cd concentration while driving long-distance Cd transport via xylem vessels. Interestingly, CAL1 does not appear to affect Cd accumulation in rice grains or the transport of other essential metals. The results provided novel insights into basic scientific issues and would essentially contribute to the practical applications of "remediation-crops".
This work entitled "A defensin-like protein drives cadmium efflux and allocation in rice" was published in Nat Commun (Luo et al., 2018, 9: 645).

Jasmonate response decay and defense metabolite accumulation contributes to age-regulated dynamics of plant insect resistance
Immunity deteriorates with age in animals but comparatively little is known about the temporal regulation of plant resistance to herbivores. The phytohormone jasmonate (JA) is a key regulator of plant insect defense. Here, the research group led by Dr. Xiaoya Chen show that the JA response decays progressively in Arabidopsis. They show that this decay is regulated by the miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) group of proteins, which can interact with JA ZIM-domain (JAZ) proteins, including JAZ3. As SPL9 levels gradually increase, JAZ3 accumulates and the JA response is attenuated. They provide evidence that this pathway contributes to insect resistance in young plants. Interestingly however, despite the decay in JA response, older plants are still comparatively more resistant to both the lepidopteran generalist Helicoverpa armigera and the specialist Plutella xylostella, along with increased accumulation of glucosinolates. The group proposes a model whereby constitutive accumulation of defense compounds plays a role in compensating for age-related JA-response attenuation during plant maturation.
This work entitled "Jasmonate response decay and defense metabolite accumulation contributes to age-regulated dynamics of plant insect resistance" was published in Nat Commun (Mao et al., 2017, 8: 13925).

The molecular basis of flowering time in perennial plants
Plants have different life forms, such as annual, biennial and perennial. Most polycarpic perennials flower over many seasons in their lifetime. How perennials undergo repeated cycles of vegetative growth and flowering is poorly understood.
Cardamine flexuosa, a member of the Brassicaceae, is a herbaceous perennial. C. flexuosa has an obligate requirement for a week- to month-long cold temperature, a treatment known as vernalization, to induce flowering. The plants younger than 4 weeks old could not respond to cold. The research group led by Dr. Jiawei Wang revealed that the levels of two microRNAs (miRNAs) contribute to regulates the timing of acquisition of floral competence in response to cold treatment in C. flexuosa. Floral induction is achieved only when the old plants are exposed to cold for at least two months.
Mechanismly, age and cold coordinate to regulate floral induction in C. flexuosa by removal of two repressors, CfFLC, which is repressed by cold treatment, and CfTOE1, which is down-regulated by the miR156-SPL-miR172 cascade. In the young seedling, high levels of miR156 lead to the accumulation of CfTOE1. CfTOE1 represses CfSOC1 expression regardless of cold treatment; as the plant grows, the endogenous sugar content is elevated, resulting in a decreased level of miR156 and the concomitant increase in miR172. As a consequence, the occupation of CfTOE1 at CfSOC1 promoter was reduced, leading to a "cold-sensitive" state. Flowering can be successfully induced when CfFLC expression is reduced by cold treatment.
The integration of age and cold response offers advantage for perennial growth habit, by ensuring plants do not flower until they develop axillary shoots and gain enough biomass. The study also suggests that the species-specific imbalance of repressive versus inductive floral inductive signals determines the life cycle strategy of flowering plants.
This work entitled "Molecular basis of age-dependent vernalization in Cardamine flexuosa" was published in Science (Zhou et al., 2013, 340: 1097-1100).

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