Grand Challenges: Nitrogen Use

Question 1

Importance of N

Answer 1

Need for amino acids and protein
Too few = stunted growth & chlorotic leaves

Reduction of nitrate to ammonia in soil
Taken up and incorporated into amino acids and proteins

Question 2

Fixing N

Answer 2

Nitrogenase enzyme
Free living species or associated w plants
Energy source needed

Question 3

Nitrogenase sensitivity

Answer 3

Sensitive to oxygen - causes deactivation
Large energy input from ATP and reductant

Question 4

Root nodules

Answer 4

1/3 of photosynthetic production supports nodules - expensive for host plant
Microbes exchange ammonia for carbon and sucrose

Question 5

Engineer nodules into non-legumes

Answer 5

Reduce need for fertiliser
Tradeoffs w yield due to high energy requirement

Question 6

Comparative genomics

Answer 6

Lots of plants already have system - trigger what’s already there

Question 7

Signalling

Answer 7

Plant to microbes - flavinoids
Microbes to plants - nod factors

Question 8

Next gen sequencing

Answer 8

Sequence genomes of plants through diff phyla that interact w microbes
Identify genes lost and gained in evolution - which genes underpin changes and key switches in genomes
Target genes - find regulator that can turn on genes already there

Question 9

Lateral roots

Answer 9

Branches in root system to explore soil and get nutrients
Similar genes to making nodules so most plants have it - turn on at right time to make nodule instead of lateral roots

Question 10

Making lateral roots

Answer 10

Start from pericycle (inner layer next to vascular tissue)
Linked to accumulation of auxin in pericycle - triggers cell division and outwards growth
Direct fluc of auxins using PIN proteins

Question 11

PIN proteins

Answer 11

Direct auxin flow out of particular edge of cell - align in straight line to get a straight lateral root

Change in pattern of PIN proteins causes change in direction of auxin flow
Bulging where lateral root bud forms
Triggers developmental processes