Table 1 An evolutionary view - vegetative desiccation tolerance in plants

Liverworts/

Rapid desiccation tolerated;

Anatomically primitive

Cell integrity maintained during drying

hornworts/

Some protection mechanisms

No vasculature

Rehydration leads to damage

mosses

focus on repair mechanisms

Rapid recovery

photosynthetic-apparatus maintained

Presence of non-reducing sugars, dehydrins and

   rehydrins appear

Pre-stress existence of mRNA in RNPs

Selaginellales,

Slower desiccation required;

Vascular tissues develop

Isoetales,

photosynthetic-apparatus maintained

Scarcity of data

Lycopodiales

Epidermis appears

Equisetum/

Slow desiccation required

Increasing anatomical and

Scarcity of data

Ferns

   developmental complexity

Epidermis appears

Gymnosperms

No vegetative desiccation

Beginning seed desiccation

Scarcity of data

   tolerance

   tolerance

Angiosperms

(Re)-discovery of vegetative

Established seed desiccation

Transcripts for proteins typical for drying

   desiccation tolerance

   tolerance

   seeds induced in vegetative tissues

Monocots

Slow desiccation required

Transcripts of unknown function homologous

   Poaceae

Focus on protection of

   to constitutively expressed moss genes

   Liliaceae

   existing structures

   are induced

Dicots

Photosynthetic-apparatus either maintained

LEA proteins, sugars and oligosaccharides,

   Hamamelidaceae

   or reduced during desiccation

Dehydrins and rehydrins in complex gene families

   Labiatae

Tolerance inducible, ABA influence, sugars may be

   Gesneriaceae

   present or inducible

   Scrophulariaceae

Transcription factors, vesicular traffic