Targeting cyanobacterial bicarbonate transporters to C3 chloroplasts – What does it take?

Date

Tuesday 28 June 2016

Time

12:30-13:30

Venue

CSIRO Black Mountain B1 Lecture Theatre

Speaker

Dr. Vivien Rolland, CSIRO Agriculture & Food, ACT

Synopsis

Most major crops used for human consumption are C3 plants, which yields are limited by photosynthetic inefficiency. To circumvent this, it has been proposed to implement the cyanobacterial CO2-concentrating mechanism (CCM), principally consisting of bicarbonate transporters (BicA and SbtA) and carboxysomes, into plant chloroplasts. As it is currently not possible to recover homoplasmic transplastomic monocots, foreign genes must be introduced in these plants via nuclear transformation. Consequently, it is paramount to ensure that resulting proteins reach the appropriate sub-cellular compartment, which for BicA and SbtA, is the chloroplast inner-envelope membrane (IEM). Prior to this work, signals to target large transmembrane proteins from non-chloroplastic organisms to plant chloroplast envelopes were unknown. In this talk, I will (1) compare the targeting requirements of soluble and transmembrane proteins, (2) explore the role of different protein domains involved in IEM-targeting of Arabidopsis proteins, and (3) present how we utilised this acquired knowledge to demonstrate that nuclear-encoded transmembrane proteins from non-chloroplastic organisms can be targeted to C3 chloroplasts; a finding which represents an important advance in chloroplast engineering by opening up the door to further manipulation of the chloroplastic envelope.