UNASSIGNED: Plant hybrids are extensively used in agriculture to deliver increases in yields, yet the molecular basis of their superior performance (heterosis) is not well understood. Our transcriptome analysis of a number of @entity958 F1 hybrids identified changes to defense and stress response gene expression consistent with a reduction in basal defense levels. Given the reported antagonism between plant immunity and growth, we suggest that these altered patterns of expression contribute to the greater growth of the hybrids. The altered patterns of expression in the hybrids indicate decreases to the @entity3785 (SA) biosynthesis pathway and increases in the auxin [ @entity9634 ( @entity6207 )] biosynthesis pathway. SA and @entity6207 are hormones known to control stress and defense responses as well as plant growth. We found that @entity6207 -targeted gene activity is frequently increased in hybrids, correlating with a common heterotic phenotype of greater leaf cell numbers. Reduced SA concentration and target gene responses occur in the larger hybrids and promote increased leaf cell size. We demonstrated the importance of SA action to the hybrid phenotype by manipulating endogenous SA concentrations. Increasing SA diminished heterosis in SA-reduced hybrids, whereas decreasing SA promoted growth in some hybrids and phenocopied aspects of hybrid vigor in parental lines. @entity3437 @entity281 of hybrids demonstrated that the reductions in basal defense gene activity in these hybrids does not necessarily compromise their ability to mount a defense response comparable to the parents.

Hormone-regulated defense and stress response networks contribute to heterosis in XXXX F1 hybrids.

@entity6207 :: ('CHEBI:16411', 'Chemical') :: ['IAA'] @entity3785 :: ('MESH:D020156', 'Chemical') :: ['salicylic acid'] @entity958 :: ('3702', 'Species') :: ['Arabidopsis'] @entity281 :: ('MESH:D007239', 'Disease') :: ['infection'] @entity3437 :: ('317', 'Species') :: ['Pseudomonas syringae'] @entity9634 :: ('MESH:C030737', 'Chemical') :: ['indole-3-acetic acid']
@entity958 :: (3702,Species) :: ['Arabidopsis']
