Exploring regulatory networks of secondary cell wall formation during vessel development in monocots and dicots

Plant Breeding, Genetics, and Biotechnology Division Seminar

By Lutz Neumetzler
Visiting research fellow
Plant Breeding, Genetics, and Biotechnology Division
IRRI

1400 H, Wednesday, 17 October 2012
Room A, D.L. Umali Building

Abstract:

Plant cell walls provide rigidity, shape the habitus of an organ, and, in turn, form the plant body. They are designed to fulfill a variety of functions, among them, water and nutrient transport in heights up to 100 meters, resisting enormous negative pressure. During the life of the plant, different phases such as cell division, cell expansion, and cell differentiation require the cell wall to be flexible, expandable, and strong at the same time. This is achieved by a dynamic interplay between cell wall-synthesizing glycosyltransferases located in the Golgi Apparatus and in the Plasmamembrane; and glycosylhydrolases that remodel and fine-tune cell wall structure in the apoplast. Plant cell walls are comprised mostly of carbohydrate polymers and are thus one of the biggest sink compartments in the plant body. These fixed energy and carbon resources can be used in sustainable ways. In order to ease saccharification or deconstruction of cell walls for, e.g., bioethanol production, we attempted to understand regulatory and developmental programs by modifying receptor-like kinases and transcription factors in planta. Within the European consortium initiative Knowledge Based Bio-Economy (KBBE), Arabidopsis and Brachypodium distachyon, an annual grass model species, were used in a study to compare cell wall metabolism in monocots and dicots.

Time of anthesis in response to environmental conditions in rice (Oryza sativa)

CESD Seminar

By Cécile Julia
Engineer in plant breeding; Ph.D. student in rice ecophysiology, CIRAD-AGAP, Montpellier, France Ph.D. research scholar, Crop Physiology Unit
Crop and Environmental Sciences Division (CESD), IRRI

1315-1415 H, Tuesday, 26 June 2012
Room A, D.L. Umali Auditorium, IRRI

Abstract:

Thermal stress and in particular heat during anthesis causes sterility in rice inflorescences. Rice spikelets open in the morning and close a few hours later. Genotypic variation in the time of day of anthesis is considered an escape mechanism from thermal stress, but little is known on its dependency on environmental conditions. 

One traditional, cold-tolerant rice cultivar and three improved tropical rice cultivars were grown in the field in four different climatic environments under flooded conditions to study the environmental response of time of day of anthesis. The time of day when the first spikelets opened, a maximum of spikelets were open and the last spikelets closed was observed daily on a population basis (2m² plots replicated 3 times).

Within the same environment, genotypic differences in time of anthesis and duration of anthesis were small. Across all genotypes and environments, the differences were broader and 80% of the variation of the time of maximum anthesis could be explained with the mean minimum air temperature (Tmin) during the 7 days preceding any given anthesis event. Linear, multiple regression models determined for each cultivar using Tmin and vapor pressure deficit (VPD) observations from the three tropical environments explained 94% of variation of time of anthesis onset and end. Low Tmin thereby delayed and low VPD advanced anthesis processes.

Under the assumption that panicle temperature during anthesis is indeed a major determinant of spikelet fertility in rice, it is concluded that the sensitivity of time of day of anthesis to air temperature and humidity is an effective eco-physiological adaptation of the rice crop.