Leaf vein pattern response to heat and drought requires genes that influence PINFORMED1 localization and is mimicked by ABA treatment

We show that Arabidopsis leaf vein pattern responds to heat or drought by increasing vein density and vein meetings. When genes ( FORKED1 , FORKED-LIKE1, 2, 3 and UNHINGED ) that control PINFORMED1 localization and leaf vein pattern are mutated, the leaf vein pattern response to heat and drought is reduced or eliminated, indicating that these genes, and possibly PINFORMED1 localization and auxin transport, are important factors in the environmental response. The vein pattern response is mimicked by treatment with ABA. As shown by the dotted arrow and question mark, this may indicate that ABA mediates the vein pattern response to heat and drought. Interestingly, the vein pattern of forked1 mutants responds to ABA, suggesting that ABA works independently of FORKED1 and possibly other vein pattern genes. • In response to heat or drought, Arabidopsis leaves increase leaf vein density. • In response to heat, Arabidopsis leaves form more vein connections. • Treatment with abscisic acid mimics the heat and drought response. • Mutations in genes that control vein pattern via PIN1 reduce the response. • An open vein pattern prevents shoot nitrogen increases under drought. The plasticity of plant development allows acclimation to environmental stresses such as heat and drought. For example, increased vein density with more vein meetings is proposed to provide more efficient and robust water delivery when water availability is reduced. We demonstrate that Arabidopsis leaves respond to short term heat or drought by increasing leaf vein density, which in heat includes a higher density of vein meetings. We find that a set of genes, UNHINGED , FORKED1 , FORKED-LIKE1 , 2 and 3 , which influence PINFORMED1 localization and control vein meeting in developing leaves, is required for the vein pattern response to heat or drought. Comparison of δ 13 C (‰) and nitrogen (%) under different conditions suggests that while wild type and mutant genotypes enriched δ 13 C (‰) under drought conditions, only wild type increased total shoot nitrogen suggesting increased photosynthetic assimilation. One explanation is that the mutants’ open vein pattern fails to supply sufficient water to support increased photosynthesis. Finally, treatment with ABA caused changes to leaf vein pattern similar to heat or drought treatment, a response that was eliminated in the abscisic acid insensitive1 but not the forked1 genotype. This suggests that the vein pattern response to reduced water availability may in part be controlled by ABA.