Loss of PIF7 attenuates shade and elevated temperature responses throughout the lifecycle in Pennycress

Pennycress ( Thlaspi arvense ) is under development to be grown as a winter annual intermediate oil seed bioenergy crop in the Midwest during typical fallow periods. Crucial work remains to domesticate and optimize pennycress for incorporation into cropping systems and increasing resilience to rising temperatures. We found that increased planting density reduces biomass and swiftens time to flowering and maturity, which are features associated with shade avoidance responses. In controlled conditions, we found that pennycress elongates in response to foliar shade and increased ambient temperatures (20 °C to 28 °C). We applied the knowledge base from Arabidopsis thaliana to manipulate genes in the PHYB signaling pathway to simultaneously decrease the shade avoidance response during interseeding and tissue responses to elevated temperatures. Evaluation of CRISPR alleles of PIF7 shows that pif7 reduces organ elongation to competition and heat cues and retains a compact rosette when exposed to shade or elevated temperature and their combination. Crucially, yield and oil content were unaltered in pif7 and plants maintained earlier flowering in stress conditions. Furthermore, indicators of plant health, such as hue, chlorophyll indices, and root system architecture were improved between wild type and pif7 . This is evidence that plant architecture and physiological health can be uncoupled under competition and heat conditions, supporting our efforts to attenuate morphological responses to environmental cues. We propose this strategy to reduce SAR will improve pennycress performance at high densities, during interseeding establishment in standing crops, and in a warming climate.