Data from: Increased growth in sunflower correlates with reduced defenses and altered gene expression in response to biotic and abiotic stress

Cultivated plants have been selected by humans for increased yield in a relatively benign environment, where nutrient and water resources are often supplemented, and biotic enemy loads are kept artificially low. Agricultural weeds have adapted to this same benign environment as crops, and often have high growth and reproductive rates, even though they have not been specifically selected for yield. Considering the competing demands for resources in any plant, a key question is whether adaptation to agricultural environments has been accompanied by life-history trade-offs, in which resistance to (largely absent) stress has been lost in favor of growth and reproduction. The experiments reported here were designed to test for growth-defense trade-offs in agricultural weeds, crops, and native varieties of common sunflower (Helianthus annuus L., Asteraceae) by comparing their performance in the presence or absence of abiotic (drought and crowding) or biotic (simulated herbivory, insect herbivory, and fungal) stress. We found that growth, as well viability of crops and weeds, were reduced by abiotic drought stress. The weakened defense in the agricultural genotypes was further evident as increased susceptibility to fungal infection and higher level of insect palatability. To uncover molecular mechanisms underlying these trade-offs we monitored gene expression kinetics in drought-stressed plants. By correlating phenotypic observations with molecular analyses, we report the identification of several genes, including a protein phosphatase 2C and the HD-Zip transcription factor Athb-8, whose expression is associated with the observed phenotypic variation in common sunflower.

栽培植物经人类定向选育，以在相对温和的农业环境中提升产量——此类环境通常会人工补充养分与水资源，并压低生物天敌的种群压力。农田杂草与作物一样，已适应这类温和的农业环境，即便未经过针对产量的特异性选育，仍普遍具备较高的生长与繁殖速率。考虑到任何植物均存在资源竞争需求，一个核心科学问题在于：对农业环境的适应是否伴随生活史权衡——即针对（基本已消失的）胁迫的抗性丧失，转而偏向生长与繁殖。本研究所述实验旨在检验农田杂草、作物及普通向日葵（Helianthus annuus L.，菊科）原生品种间的生长-防御权衡关系，通过对比它们在施加与未施加非生物（干旱与种群拥挤）或生物（模拟植食、昆虫植食与真菌）胁迫时的表现展开。研究发现，非生物干旱胁迫会抑制作物与杂草的生长及其存活力。农业基因型的防御能力弱化现象进一步体现为：对真菌侵染的易感性提升，以及对昆虫的适口性增强。为揭示上述权衡现象背后的分子机制，本研究对受干旱胁迫的植株开展了基因表达动力学监测。通过将表型观测结果与分子分析相结合，本研究鉴定出多个与普通向日葵观测到的表型变异相关的基因，其中包括蛋白磷酸酶2C（protein phosphatase 2C）以及HD-Zip转录因子Athb-8。